LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 
Clots 


THE 

INDUSTRIAL  AND  ARTISTIC 

TECHNOLOGY 


OF 


PAINT   AND    VARNISH 


BY 

ALVAH    HORTON    SABIN,    M.S., 

CHEMIST    FOR    EDWARD    SMITI!    &    Co.,    NEW   YORK. 

Member  of  the  American  Chemical  Society,  the  American  Society  of  Mechanical  Engineers, 

the  American  Society  for  Testing  Materials,  the  Society  of  Arts  (London);  Associate 

Member  of  the   American   Society   of  Civil  Engineers;    Lecturer  in   New 

York    University  and  the   Massachusetts   Institute   of   Technology; 

lately  Professor  of  Chemistry  in  the  University  of  Vermont. 


FIRST    EDITION-. 
FIRST    THOUSAND. 


NEW   YORK: 

JOHN    WILEY    &    SONS. 
LONDON:    CHAPMAN   &    HALL,  LIMITED. 
1904. 


Copyright,  1904, 
BY 

'ALVAH  HORTON  SABIN. 

Entered  at  Stationers'*  Hall,  London. 


ROBERT  DRUMMOND,    PRINTER,  NEW   YORK. 


PREFACE. 


THE  wise  Quintilian  remarked,  that  "If  we  can  say  what  is 
right  we  shall  be  delighted,  though  it  may  not  be  of  our  own 
invention."  This  observation  may  well  serve  as  a  text  for  any 
one  who  speaks  of  a  technical  art,  such  arts  being  of  slow  growth, 
so  that  an  account  of  any  of  them  concerns  itself  much  with  the 
past,  and  the  knowledge  of  the  expert,  as  a  bookmaker,  is  largely 
valuable  for  separating  the  true  and  the  significant  from  that 
which  is  untrue,  or  if  true  is  of  no  relevancy  or  use.  To  no  art 
does  this  apply  more  than  to  that  which  concerns  the  making 
and  using  of  protective  and  decorative  coatings,  which  have 
been  used  from  remote  times;  sometimes,  though  perhaps  empir- 
ically, in  ways  analogous  or  closely  similar  to  the  most  approved 
modern  practice,  then  wandering  off  into  the  use  of  inefficient, 
irrational,  and  unsatisfactory  methods  and  materials. 

The  aim  of  the  writer  is  to  give  a  correct  general  outline 
of  the  subject  of  Paints  and  Varnishes,  with  a  brief  account 
of  their  modern  use  and  of  the  principles  which  are  involved  in 
their  fabrication  and  application.  Many  of  the  facts  herein 
noted,  though  old,  are  practically  unknown,  and  some  of  them 
exactly  anticipate  recently  patented  processes;  their  value  to 
the  public  in  that  way  is  sufficient  excuse  for  their  republication. 
Scarcely  any  patents  in  this  line  are  of  any  value  or  validity; 
and  the  ''secret  processes"  which  are  continually  vended  are  for 
the  most  part  neither  secret  nor  new.  The  only  trade  secrets  lie 
in  the  incommunicable  intimate  knowledge  of  the  expert,  and 
are  made  valuable  only  by  his  unceasing  care,  vigilance,  and. 


v  PREFACE. 

conscientiousness.  Theories  may,  however,  be  made  known, 
,and  the  attention  of  the  student  may  be  intelligently  directed  to 
their  application. 

The  author  foresees  that  one  criticism  of  this  work  will  be 
on  the  importance  assigned  to  the  use  of  oleo-resinous  varnishes. 
He  can  only  say  in  reply  that  if  he  had  the  courage  of  his  con- 
victions it  would  have  been  made  a  great  deal  more  prominent 
than  it  is,  and  that  the  daily  study  of  new  problems,  as  well  as 
systematic  observation  of  the  results  of  work  done  many  years 
ago,  produces  in  his  mind  the  belief  that  it  is  in  this  direction 
we  must  look  for  future  progress. 

Apology  is  perhaps  due  the  reader  for  the  lack  of  a  very  co- 
herent plan  in  this  treatise.  In  part  the  contents  of  this  book 
.are  those  things  which  seem  most  interesting  or  important  to 
the  writer;  in  part  they  are  things  which  long  practical  experi- 
ence has  shown  to  interest  many  other  people.  Things  which 
many  people  will  wish  to  know  are  left  out,  in  many  cases  because 
of  the  limitations  of  the  author's  knowledge,  but  often  because 
the  book  is  already  too  large;  and  to  all  the  writer  commends 
the  amiable  maxim  of  Erasmus,  that  "a  reader  should  sit  down 
to  a  book  as  a  polite  diner  does  to  a  meal.  The  entertainer 
tries  to  satisfy  all  his  guests;  but  if  it  should  happen  that  some- 
thing does  not  suit  this  or  that  person's  taste  they  politely  conceal 
their  feelings  and  commend  other  dishes,  that  they  may  not  dis- 
tress their  host." 


CONTENTS. 


CHAPTER    I. 

PAGE 

INTRODUCTORY i 

CHAPTER   II. 
EARLY  HISTORY 0 6 

CHAPTER   III. 
VARNISH  :  ORIGIN  OF  THE  NAME 27 

CHAPTER  IV. 
LINSEED-OIL 31 

CHAPTER  V. 
LINSEED-OIL.     BY  DR.  PARKER  C.  MC!LHINEY  39 

CHAPTER  VI. 
MANUFACTURE  OF  VARNISH 71 

CHAPTER   VII. 
TUNG-OIL 85 

CHAPTER  VIII. 
JAPANS  AND  DRIERS. 87 

CHAPTER   IX. 

ROSIN 95 

• 

CHAPTER   X. 

SPIRIT  VARNISHES 103. 

v 


VI  CONTENTS. 

CHAPTER   XI. 

PAGE 

PYROXYLIN  VARNISHES 112 

CHAPTER  XII. 
OIL-PAINTS  AND  PAINTS  IN  JAPAN 1 1 8 

CHAPTER   XIII. 
VARNISH  OR  ENAMEL  PAINTS 140 

CHAPTER   XIV. 
CHINESE  AND  JAPANESE  LACQUERS 146 

CHAPTER    XV. 
PROTECTION  OF  METALS  AGAINST  CORROSION 180 

CHAPTER   XVI. 
WATER-PIPE  COATING 258 

CHAPTER  XVII. 
SHIP'S-BOTTOM  PAINTS 290 

CHAPTER  XVIII. 
SHIP-  AND  BOAT-PAINTING 297 

CHAPTER  XIX. 
CARRIAGE-PAINTING  ...   301 

CHAPTER  XX. 
HOUSE-PAINTING 311 

CHAPTER  XXI. 
FURNITURE-VARNISHING 327 

CHAPTER   XXII. 

CONCLUSION  — 340 

INDEX 365 


TECHNOLOGY  OF  PAINT  AND  VARNISH 


CHAPTER  i. 

INTRODUCTORY. 

WHEN  we  devote  our  attention  to  the  subject  of  paint  and 
painting,  we  seem  to  encounter  matters  on  which  the  vast  major- 
ity of  commonly  well-educated  people  feel  almost  entire  ignorance 
and  concerning  which  the  opinion  of  any  self-constituted  expert 
is  allowed  to  carry  a  weight  which  is  out  of  all  proportion,  in 
most  instances,  to  its  real  value.  In  reality,  although  there  are 
many  special  cases  where  expert  opinion  is  needed,  and  not  a  few 
where  the  most  learned  and  practised  must  feel  uncertain,  the 
general  principles  involved  are  not  difficult  to  understand,  and 
should  be  known  to  any  one  who  is  interested  in  the  practical 
matters  of  every-day  life.  The  lack  of  such  knowledge  is  a 
source  of  discomfort  and  unnecessary  expense  to  not  a  few  who 
are  the  victims  of  the  ignorance  and  cupidity  of  those  whom  they 
employ.  Very  many  people  have  a  fair  practical  knowledge 
of  carpentry,  for  instance,  so  as  to  be  able  to  detect  poor  work- 
manship, although  unable  to  do  such  work  themselves;  some 
have  such  a  knowledge  of  plumbing;  but  few  feel  qualified  to 
critically  examine  a  job  of  painting  and  varnishing,  yet  almost 
everything  which  we  touch  or  use  has  been  in  some  way  or 
some  part  treated  with  a  protective  or  decorative  coating. 

The  beginner,  who  will  probably  find  this  book  more  helpful 


2  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

and  suggestive  than  any  one  else,  since  the  author  cannot  hope 
to  instruct  the  expert,  must  begin  at  the  beginning,  that  is  to  say, 
with  a  brief  description,  correct  so  far  as  it  goes,  of  the  most 
essential  materials  and  processes  employed  in  the  art,  which 
having  learned,  discussion  of  more  detailed  matters  may  be  un- 
derstood and  the  consideration  of  the  more  complex  or  difficult 
compounds  or  methods  will  be  left  to  later  chapters.  Let  us 
consider,  then,  which  first,  paint  or  varnish?  It  is  difficult  to 
decide;  like  the  celebrated  problem  of  the  bird  and  the  egg: 
"When  I  consider  the  beauty  of  the  complete  bird,"  said  the 
owl,  "I  think  that  must  have  been  first,  as  the  cause  is  greater 
than  the  effect;  when  I  remember  my  own  childhood,  I  incline 
the  other  way."  Painting  is  not  complete  without  varnish.  Var- 
nish is  an  ingredient  of  most  paint,  but  paint  is  often  thought  of 
as  the  foundation  and  varnish  as  the  finish.  It  does  not  matter 
much ;  let  us  tell  first  about  varnish. 

Varnish:  Definition. — As  the  term  is  commonly  used,  this 
is  a  substance  which  is  applied  as  a  liquid,  and  on  exposure  to 
the  air  hardens  and  forms  a  thin  and  usually  somewhat  trans- 
parent film  (but  some  varnishes  are  black  and  nearly  opaque), 
which  improves  or  better  displays  the  surface  over  which  it  is 
spread  and  to  a  considerable  degree  protects  it  from  dirt  and 
injury.  Some  varnishes  harden  by  a  chemical  change,  which  in 
almost  all  cases  is  the  absorption  of  oxygen  from  the  air,  others 
by  the  evaporation  of  the  solvent.  The  former  are  the  most  im- 
portant and  are  made  from  certain  resins,  known  as  varnish- 
resins  or  varnish-gums  (though  not  gums  in  the  strict  sense,  but 
commercially  so  called),  and  linseed-oil.  They  are  thinned  with 
spirits  of  turpentine.  The  process  of  manufacture  is  briefly  as 
follows : 

Varnish:  How  Made. — The  resin  is  .put  in  a  copper  kettle, 
which  is  then  put  over  a  hot  fire  until  the  resin  is  thoroughly 
melted.  The  linseed-oil  is  then  added  and  the  mixture  is  heated 
until  the  ingredients  are  well  combined.  It  is  then  partially 
cooled  and  is  thinned  with  enough  spirits  of  turpentine  to  make 
it  thin  enough  for  use  when  cold.  When  such  a  varnish  is  spread 


INTRODUCTORY.  3 

over  a  surface  with  a  brush  or  otherwise  it  forms  a  thin  film, 
not  more  than  a  few  thousandths  of  an  inch  in  thickness,  and  of 
course  exposes  a  great  deal  of  surface  to  the  air.  What  first 
happens  is  that  the  turpentine  evaporates,  then  the  oil  and  resin 
compound  absorbs  oxygen  and  is  converted  into  a  hard,  glossy 
film.  This  may  take  a  few  hours  or  a  few  days. 

Upon  a  little  reflection  it  will  be  obvious  that  the  relative 
amounts  of  oil  and  resin  will  be  an  important  factor  in  deter- 
mining the  quality  of  the  compound;  also,  since  the  oil  and  tur- 
pentine are  always  of  about  the  same  quality,  while  the  resins 
vary  considerably,  that  the  kind  of  resin  used  will  be  of  impor- 
tance ;  and  that  different  sorts  of  varnishes  may  be  made  for 
different  uses. 

Spirit  Varnish. — Varnishes  of  another  kind  are  made  by 
dissolving  the  resin  (or  other  substance,  but  resins  are  chiefly 
used)  in  a  volatile  liquid  such  as  alcohol.  Such  a  varnish,  when 
spread  over  a  surface,  loses  its  solvent  by  evaporation,  and  the 
resin  is  then  found  in  a  thin  uniform  film,  the  liquid  having  served 
as  a  mechanical  means  of  uniformly  spreading  the  resin  over  the 
surface  to  be  coated. 

Linoxyn. — If  we  spread  a  film  of  lard-oil  or  cottonseed-oil 
over  a  non-absorbent  surface,  such  as  a  piece  of  glass,  and  expose 
it  to  the  air,  it  does  not  seem  to  change,  at  least  not  for  a  long 
time.  The  surface  is  simply  made  greasy;  but  if  we  use  linseed- 
oil  in  the  same  way,  after  a  short  time,  or  at  most  within  a  few 
days,  we  find  that  a  remarkable  change  has  taken  place.  The 
film  is  no  longer  a  greasy  fluid,  but  is  a  tough,  leathery,  solid  sub- 
stance, not  in  the  least  like  oil.  This  new  material  has  been 
formed  by  the  absorption  of  oxygen  by  the  oil  and  is  known  as 
oxidized  oil,  or  linoxyn.  This  capacity  for  change  into  a  tough 
and  permanent  solid  substance  by  the  action  of  the  air  is  an 
unusual  and  valuable  quality,  which  causes  linseed-oil  to  be 
chosen  for  making  paint  or  varnish.  In  fact,  the  film  of  dried 
oil  without  any  addition  of  resin  is  a  sort  of  varnish,  and  in  some 
countries  is  commonly  spoken  of  as  oil  varnish.  Such  a  film  is 
pale  yellow  in  color,  nearly  transparent,  like  most  varnish-films, 


4  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

and  if  it  is  desired  to  apply  a  colored  film  it  is,  of  course,  necessary 
to  add  some  color  to  it. 

Pigments.— This  is  done  by  mixing  with  the  oil  or  varnish, 
while  it  is  a  liquid  and  before  it  has  been  spread  over  the  surface 
to  be  coated,  a  colored  pigment  which  is  a  solid  substance,  such, 
for  example,  as  a  piece  of  colored  rock  which  has  been  ground 
to  a  fine  powder.  This  pigment  does  not  dissolve  in  the  oil  but 
only  mixes  with  it,  converting  it  into  a  muddy,  opaque,  colored 
liquid,  of  course  of  a  thicker  consistence  than  the  pure  oil  or 
varnish. 

Paint. — When  this  mixture,  which  is  called  paint,  is  spread 
out  hi  a  thin  film  the  oil  or  varnish  hardens,  as  has  been  described, 
and  acts  as  a  cementing  material,  or  binder,  to  hold  the  particles 
of  pigment  on  the  surface  which  has  been  coated.  But  oil  and 
varnish  are  not  the  only  cements,  and  it  is  not  absolutely  neces- 
sary to  use  them  in  making  a  paint.  We  may  mix  the  colored 
pigment  with  a  dilute  solution  of  glue,  as  is  done  in  making  kal- 
somine,  and  such  a  mixture  is  used  in  making  water-color  or 
distemper  paintings. 

Water-colors. — There  is  no  reason  why  painting  done  in  dis- 
temper (water-color)  should  not,  after  it  gets  quite  dry,  be  var- 
nished with  any  ordinary  varnish,  to  enhance  its  beauty  and  make 
it  more  permanent,  and  in  fact  this  is  often  done  and  has  been 
from  the  earliest  times. 

Encaustic  Painting. — In  former  times  there  was  still  another 
sort  of  painting,  which  has  now  gone  out  of  practice,  called  en- 
caustic painting.  This  was  done  with  wax,  colored  by  mixing  it 
with  suitable  pigments,  applied  in  a  melted  condition,  and  some- 
times covered  with  a  varnish.  Wax  in  solution  is  still  employed 
as  a  coating,  especially  for  floors,  but  encaustic  painting  was  done 
with  melted  wax  and  the  finished  work  commonly  glazed  by  hold- 
ing a  hot  iron  or  a  torch  in  front  of  it.  Such  painting  was  very 
durable  when  not  exposed  to  heat  nor  to  the  weather,  but  could 
not  be  handled.  It  was  used  for  mural  decorations.  Instead  of 
a  spirit,  varnish,  a  powdered  resin  was  sometimes  employed, 
which  was  sifted  over  the  surface  and  fixed  by  being  melted  by 


INTRODUCTORY.  5 

the  application  of  a  hot  iron.  Sandarac  was  the  resin  used,  and 
this  was  the  old  English  pounce,  sprinkled  over  the  surface  from 
a  pouncet-box  or  pounce-box  like  a  pepper-box.  There  are  many 
other  minor  varieties  of  both  paint  and  varnish,  but  if  the  reader 
will  remember  what  has  just  been  told,  especially  the  practice  of 
making  oleo-resinous  varnishes  by  first  melting  the  resin  and  then 
adding  the  oil,  cooking  the  compound,  and  afterward  thinning  it, 
he  will  be  able  to  clearly  understand  the  modifications  and  addi- 
tions which  are  to  be  made  in  the  later  descriptions  of  a  more 
detailed  character. 


CHAPTER   II. 

EARLY  HISTORY. 

KNOWLEDGE  of  the  early  history  of  any  art  is  fragmentary 
and  apt  to  be  to  some  extent  conjectural,  but  none  the  less  inter- 
esting. It  is,  therefore,  without  apology  that  a  few  facts  are  here 
given,  not  as  a  complete  or  definite  history,  but  only  in  a  tenta- 
tive way,  as  a  possible  nucleus  about  which  other  students  with 
better  opportunities  may  group  a  more  systematic  series  of  studies, 
on  a  subject  which  appears  to  have  received  less  attention  than 
its  importance  and  intrinsic  interest  deserve. 

The  use  of  both  decorative  and  protective  coatings  is  of  great 
and  unknown  antiquity.  Savages  use  both  mineral  and  vege- 
table colors  to  decorate  their  persons,  their  clothing,  and  their 
abodes;  anointing  the  body  with  oil  as  a  protection  against  the 
weather  is  a  common  practice.  Oil  is  also  used  on  dressed 
skins  of  animals  to  make  them  pliable  and  water-proof,  and  tem- 
porary and  permanent  dwellings,  and  boats,  are  made  water- 
proof by  the  use  of  fatty  and  resinous  bodies.  When  Noah  built 
the  ark  and  coated  the  seams  with  pitch  he  was  doubtless  follow- 
ing the  most  approved  system  of  use  of  protective  coatings  on 
•structural  materials,  which  was  then  probably  of  remote  antiquity 
and  traditional  origin,  and  which  he  may  have  learned  when  he 
was  a  boy,  four  or  five  hundred  years  before. 

Grease-paints. — It  is  only  reasonable  to  suppose,  and  this  is 
borne  out  by  the  present  practice  of  savage  tribes,  that  the  earliest 
paints  may  have  been  pigments  mixed  with  grease  or  fat.  Such 
a  paint  adheres  to  the  human  skin  with  considerable  persistence, 
yet  it  may  be  removed  by  thorough  washing,  and  of  this  nature 

are  the  grease-paints  still  used  by  actors.     This  may  fairly  claim 

6 


EARLY  HISTORY.  7 

to  be  the  oldest  kind  of  paint.  When  such  a  paint  is  applied  to 
leather  or  wood  it  is  practically  impossible  to  remove  it  and 
probably  its  protective  action  is  considerable.  The  use  of  oil 
alone  as  a  preservative,  e.g.,  to  make  the  wood  of  bows  and  lances 
water-proof,  is  perhaps  a  forerunner  of  varnish,  being  closely 
allied  to  the  use  of  varnish  on  violins  and  other  musical  instru- 
ments. 

Egyptian  Varnish. — So  far  as  is  yet  known  to  the  author,  the 
oldest  varnish  in  existence  is  that  on  the  wooden  mummy-cases 
brought  from  Egypt.  This  is  probably  twenty-five  hundred  years 
old.  The  only  chemical  examination  of  this  which  has  been  pub- 
lished was  made  by  Professor  J.  F.  John,  of  Berlin,  about  1822. 
Lieutenant- General  H.  Von  Minutoli  conducted  an  exploring  ex- 
pedition in  Egypt,  and  published  an  account  under  the  title  "Reise 
zum  Tempel  des  Jupiter  Ammon,  etc.,  nach  Ober-Aegypten  in  den 
Jahren  1820-1821."  In  an  appendix  to  this  book  (which  may 
be  seen  in  the  New  York  Public  Library)  is  a  short  paper  by 
Dr.  John  describing  this  varnish,  which  he  found  to  be  insoluble 
in  water,  soluble  in  alcohol,  and  thrown  down  as  a  gummy  pre- 
cipitate by  diluting  the  alcoholic  solution  with  water.  He  con- 
cluded that  it  was  a  compound  of  resin  with  oil,  but  I  infer  that 
he  meant  a  solution  of  resin  in  an  essential  oil,  like  oil  of  cedar, 
which  is  about  the  same  as  oil  of  turpentine,  since  some  of  the 
varnishes  of  the  middle  ages  were  of  this  sort  (in  fact  they  were 
the  most  common  varnishes  in  Professor  John's  time),  and  he 
knew  that  the  Egyptians  were  able  to  make  oil  of  cedar  in  early 
times. 

Turpentine. — Herodotus,  who  visited  Egypt  about  460  B.C., 
describes  the  use  of  oil  of  cedar  for  embalming.  These  more 
common  essential  oils  were  prepared  both  by  the  Egyptians  and 
the  Greeks  before  the  invention  of  the  still.  One  of  the  earlier 
methods  was  to  put  the  crude  turpentine  in*  a  pot  and  lay  over 
the  top  of  the  pot  some  sticks  which  supported  a  fleece  of  wool. 
When  the  contents  of  the  pot  was  heated,  the  essential  oil  con- 
densed in  the  wool,  from  which  it  was  squeezed  out.  A  good 
account  of  the  early  methods  and  references  to  the  ancient  liter- 


8  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

ature  of  the  subject  is  to  be  found  in  Gildermeister  and  Hoffman's 
Volatile  Oils,  of  which  an  English  translation  has  been  made  by 
Dr.  Kremers  of  the  University  of  Wisconsin. 

The  varnish  in  question  may  be  seen  on  mummy-cases  hi  the 
Metropolitan  Museum  of  Art  in  New  York  City.  It  is  of  a  pale- 
yellow  color,  surprisingly  free  from  cracks,  very  hastily  and 
roughly  applied,  as  though  smeared  on  with  a  flat  blade.  This 
suggests  that  it  may  have  been  a  compound  of  a  resin  and  a 
fixed  oil.  We  know  that  the  ancients  of  all  nations  knew  how 
to  prepare  vegetable  oils,,  which  were  use<jj  as  food,  and  also  that 
they  raised  flax,  1a,nd  it  is  n'ot  unTT£efy  ttiaT  linseed-oil  may  have 
been  used  as  a  solvent  for  some  of  the  African  re'sins,  which  arc 
to  this  day  perhaps  the  most  important  varnish-resins.  A  var- 
nish made  with  five  or  six  parts  of  oil  to  one  of  resin  without  any 
essential  oil  as  a  solvent  would,  when  warm,  be  applied  exactly 
as  the  varnish  on  these  mummy-cases  was,  would  take,  as  that 
apparently  did,  a  partial  set  on  cooling,  having  practically  no 
flowing  quality,  and  would  be  extremely  durable.  No  other  var- 
nish is  known  to  the  author  which  would  behave  in  this  way; 
yet  this  is  largely  a  matter  of  conjecture,  no  samples  being  avail- 
able for  analysis.  This  much,  however,  is  clear,  that  the  Egyp- 
tians made  a  good  durable  varnish  which  has  stood  exposure  to 
the  air  twenty-five  hundred  years  and  still  looks  well.  If  the 
varnish,  as  they  made  it,  was  a  solution  in  oil  of  turpentine,  there 
is  no  reason  why  it  should  not  have  been  properly  thinned,  as 
it  would  then  flow  out  under  the  brush,  and  it  would  also  seem 
that  it  might  have  been  used  as  a  vehicle  for  painting,  while  in 
fact  all  their  painting  seems  to  have  been  done  with  pigments 
mixed  in  a  solution  of  glue. 

Glue  Size. — This  painting  in  size,  or  distemper,  seems  to  be 
the  oldest  which  has  come  down  to  us.  In  a  dry  climate  it  is 
very  lasting;  and  the  Egyptians  were  expert  glue-makers,  some 
of  their  glued  wood  joints  having  lasted  three  thousand  years.  I 
have  been  told  by  Mr.  Hewitt  (of  the  Cooper-Hewitt  Company) 
that  there  exist  descriptions  on  early  papyrus  rolls  of  the  Egyp- 
tian methods  of  glue-making  showing  that  they  had  the  essential 


EARLY  HISTORY.  y 

principles  of  the  present  methods,  and  made  practically  the  same 
product  as  some  of  the  best  glue  made  now. 

Wax  Paint  for  Ships. — Much  of  the  painting  done  by  the 
Romans,  as,  for  example,  at  Pompeii,  appears  to  have  been  with 
size,  or  glue  solution,  as  the  vehicle,  but  they  were  also  acquainted 
with  encaustic  painting,  where  the  colors  are  mixed  with  wax. 
Pliny  says  that  "when  it  became  the  fashion  to  paint  ships  of 
war,  a  third  method  was  introduced  of  melting  the  wax  with  fire 
and  using  a  brush.  Paint  applied  to  ships  in  this  way  cannot  be 
destroyed  either  by  the  action  of  the  sun  or  of  the  brine  or  wind." 
This  sounds  very  much  as  though  Pliny  were  copying  from  an 
early  advertisement.  It  is  curious  to  note,  as  will  be  shown 
later,  that  this  method  of  applying  a  melted  non-drying  paint  is 
still  in  extensive  use  on  the  exterior  of  ships,  and  almost  nowhere 
else.  Clarified  beeswax  was  used  in  ancient  times;  with  it  were 
mixed  coloring  matters,  and  in  this  way  were  made  paints  which 
formed  films  of  great  thickness  as  compared  with  any  ordinary 
paint-film  and,  being  practically  impervious  to  water,  were  very 
permanent  when  preserved  at  a  uniform  and  not  too  high  tem- 
perature. 

Vernix. — In  considering  the  history  of  this  subject,  it  is  first 
of  all  to  be  remembered  that  prior  to  the  seventeenth  century  the 
word  varnish  (Latin,  vernix  or  vernisium),  was  not  primarily 
used  to  mean  a  liquid  composition,  but  a  dry  resin,  which  when 
melted  and  boiled  with  linseed-oil  formed  a  liquid  called  ver- 
nice  liquida  by  the  early  Italian  writers,  and  corresponded  to  our 
modern  varnish.  This  use  of  the  term  is  analogous  to  our  use  of 
the  word  glue,  by  which  we  mean  primarily  a  dry  substance  and 
secondly  the  solution  of  the  same  ready  for  use.  The  resin  has 
always  been  regarded  as  the  essential  and  distinguishing  com- 
ponent of  varnish;  even  in  the  case  of  varnishes  made  from 
boiled  oil  alone,  it  is  common  to  speak  of  the  oil  as  being  con- 
verted into  resin. 

Painters'  Bills  in  the  Thirteenth  Century. — The  fact  that  var- 
nish was  a  dry  resin  is  shown  in  many  ways.  For  example,  in 
the  early  English  accounts  of  expenditures  for  the  king,  the 


10  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

quantity  of  varnish  is  always  noted  by  weight,  and  of  oil  by  meas- 
ure. In  the  period  of  1274  to  1277,  m  tne  early  part  of  the  reign 
of  Edward  L,  an  account,  apparently  relating  to  the  Painted 
Chamber,  contains  the  following  items: 

To  Reymund,  for  seventeen  pounds  of  white  lead Us.       X  d. 

To         ' '  "   sixteen  gallons  of  oil XVI  s. 

To         "  "   twenty -four  pounds  of  varnish  ....        XII  s. 

To  Hugo  le  Vespunt,        ' '  eighteen  gallons  of  oil XXI  s. 

To  Reymund,  "   one  hundred  leaves  of  gold Ill  s. 

To         "  "   twenty-five  pounds  of  varnish XI  s.        Id. 

To  William,  the  painter,  and   his   helper,    for   the   painting   of 

twelve  mews XXXVI  s. 

To       "          ' '        * '        for  seven  score  and  twelve  pounds  of 

green  for  the  same LXXV  s.     IV  d. 

To  Stephen  Ferron,  ' '   twenty  pounds  of  white Us. 

To       "  "  •  '   one  gallon  of  honey XII  d. 

Item,  '    one  gallon  of  white  wine Ill  d. 

small  brushes,  and  eggs Ill  d. 

yellow VI  d. 

size XII  d. 

These  accounts  clearly  show  that;  dry  substances  were  sold  by  the 
pound  and  liquids  by  weight.  The  use  of  honey,  eggs,  and  size 
was  for  distemper  painting,  in  all  likelihood.  So  also  in  the 
records  of  the  church  of  St.  Jacopo  at  Pistoja,  Italy,  in  1347,  is 
an  expense  for  one  pound  of  varnish,  soldi  VI. 

These  illustrations  could  be  largely  extended.  The  Italian 
writers  on  painting  constantly  speak  of  varnish  and  of  liquid 
vsfrnish  as  entirely  distinct.  It  appears  to  be  the  common  opin- 
ion of  the  early  writers  that  the  substance  properly  known  as 
varnish  was  amber,  which  was  the  resin  now  known  by  that 
name,  but  was  also  applied  apparently  to  some  of  the  hard  African 
resins  which  reached  Europe,  either  through  Egypt  or  from  India. 
Formerly  a  considerable  amount  of  Zanzibar  resin  reached  India 
and  was  marketed  from  that  country.  Salmasius,  the  greatest 
classical  scholar  of  the  early  part  of  the  seventeenth  century,  says 
the  term  "vernix"  was  misappropriated  to  mean  usandarac," 
because  of  the  resemblance  of  that  resin  to  amber.  Some  of  the 
dictionaries  of  the  middle  ages  say  that  vernix  is  sandarac,  and 


EARLY  HISTORY.  1 1 

that  it  was  a  dry  resin.  They  also  define  liquid  varnish  as  the 
resin  dissolved  in  oil.  My  own  belief  is  that  there  have  always 
been  different  kinds  of  varnishes,  both  the  resins  and  the  liquids, 
and  that  the  best  varnish  was  amber,  the  inferior  being  sandarac. 
The  latter  term  included  many  resins  which  appear  like  it,  and 
grade  down  to  common  rosin,  which  was  used  as  varnish  in  very 
early  times. 

Incense. — These  inferior  resins  were  commonly  spoken  of  as 
frankincense,  or  incense,  which  was  also  used  as  synonymous  with 
varnish.  Thus  we  read  of  the  application  of  incense,  or  frankin- 
cense, to  pictures  as  a  finishing  touch.  Amber  and  similar  resins 
have  always  been  costly  and  rare,  and  there  has  always  been  a 
substitution  for  them  of  common  and  cheaper  resins,  either  fraudu- 
lently or,  more  generally,  as  a  cheaper  but  sufficiently  good 
material.  Certainly,  from  the  present  time  back  as  far  as  we 
have  any  definite  history  of  varnish,  there  always  have  been  two 
well-defined  grades,  one  made  from  hard  resins,  the  other  from 
those  which  are  both  cheaper  and  more  easily  manipulated.  It 
is  in  fact  interesting  to  notice  how  varnish  recipes  go  in  pairs, 
one  for  amber  and  the  other  for  sandarac,  among  nearly  all 
writers  on  the  subject.  It  was  an  early  practice,  which  has 
probably  not  yet  become  entirely  obsolete,  to  sprinkle  powdered 
resin  over  paper  on  which  writings  or  drawings  had  been  made. 
This  served  to  fix  the  writing  and  was  sometimes  made  more 
certain  by  the  application  of  a  heated  iron.  Sandarac,  or  some 
similar  resin,  was  used  for  this  purpose,  and  the  hard  resins  like 
amber  are  not  suited  for  such  service.  As  this  use  of  sandarac 
is  of  considerable  and  probably  great  antiquity,  it  is  an  illustra- 
tion of  the  proper  use  of  these  softer  recent  resins.  Sandarac, 
mastic,  olibanum,  and  other  similar  resins  come  from  northern 
Africa  and  western  Asia  and  have,  therefore,  been  known  from 
most  ancient  times,  and  juniper  resin,  which  is  closely  allied  to 
sandarac  and  has  been  used  for  it,  is  very  widely  distributed. 

Treatise  of  Theophilus. — The  earliest  important  treatise  of 
the  middle  ages  on  technology  is  the  Schedula  Diversarum 
Artium  of  Theophilus  Presbyter,  a  German  or  Swiss  monk. 


12 


TECHNOLOGY  OF  PAINT  AND    VARNISH. 


There  exist  several  MS.  copies  of  this  work,  from  which  trans- 
lations have  been  made,  the  most  recent  of  which  was  by  Dr. 
Albert  Ilg  of  Vienna,  1874,  by  whom  the  various  authorities  and 
commentators  have  been  carefully  studied.  Ilg  thinks  Theophilus 
wrote  in  the  eleventh  century.  Lessing,  who  also  studied  The- 
ophilus, regards  him  as  belonging  to  the  tenth  century  and  to  have 
been  identical  with  Tutilo,  a  monk  of  the  monastery  of  St.  Gall, 
Switzerland.  The  name  Tutilo,  or  Tuotilo,  is  said  to  be  the  same 
as  Theophilus.  Many  monasteries  of  the  middle  ages  gained 
celebrity  by  the  skill  of  their  artists,  and  that  of  St.  Gall  was 
especially  distinguished  in  this  respect,  Tutilo  and  Notker,  monks 
of  this  convent,  being  the  most  celebrated  painters,  sculptors, 
and  gold-workers  of  their  time  in  Germany.  Tutilo  was  con- 
temporary with  the  Abbot  Salorno  of  St.  Gall,  and  made  for 
him  a  golden  crucifix  of  wonderful  workmanship.  Ekkehard 
speaks  of  Tutilo  as  "mirificus  aurifex."  He  was  also  musician, 
poet,  orator,  and  statesman.  The  Emperor  Charles  the  Thick 
complained  that  such  a  man  should  be  shut  up  in  a  convent. 
However  this  may  be,  the  treatise  in  question  is  not  later  than 
the  eleventh  century  and  it  does  not  claim  to  be  original,  but  to 
be  a  digest  of  standard  and  well-known  methods  and  processes. 
It  quotes  largely  from  an  earlier  work  of  the  same  kind  by  Erac- 
lius,  and  some  of  the  recipes  are  in  the  Lucca  MS.  of  the  eighth 
century.  Eraclius  collected  formulae  as  far  back  as  Dioscorides, 
early  in  the  first  century. 

His  Formula  for  Varnish. — Theophilus  gives  a  formula  for 
making  varnish  as  follows: 


Pone  oleum  in  ollam  novam 
parvulam  et  adde  gummi  quod 
vocatur  fornis,  minutissime  tri- 
tum,  quod  habet  speciem  luci- 
dissimi  thuris,  sed  cum  frangitur 
fulgorem  clariorem  reddit ;  quod 
cum  super  carbones  posueris, 
coque  diligenter  sic  ut  non  bul- 


Put  some  linseed-oil  into  a 
small  new  jar,  and  add  some  of 
the  gum  which  is  called  fornis 
(varnish),  very  finely  powdered, 
which  has  the  appearance  of  the 
most  transparent  frankincense, 
but  when  it  is  broken  it  gives 
back  a  more  brilliant  lustre; 


EARLY  HISTORY. 


liat,  donee  tertia  pars  consuma- 
tur;  et  cave  a  flamina,  quod 
periculosum  est  nimis,  et  diffi- 
cile extinguitur  si  accendatur. 
Hoc  glutine  omnis  pictura  super 
linita  lucida  fit  et  decora  ac 
omnino  durabilis.  Compone 
quatuor  vel  tres  lapides  qui 
possent  ignem  sustinere  ita  ut 
resiliant  et  super  ipsos  pone 
ollam  rudem,  et  in  earn  mitte 
supradictum  gummi  fornis,  quod 
Romana  glassa  vocatur,  et  su- 
per os  hujus  ollae  pone  ollam 
minorem,  quae  habeat  in  fundo 
modicum  foramen.  Et  circum- 
lineas  ei  pastam,  ita  ut  nihil 
spiraminis  inter  ipsos  ollas  exeat. 
Habebis  etiam  ferrum  gracile 
manubrio  impositum,  unde  com- 
movebis  ipsum  gummi,  et  cum 
quo  sentire  possis  ut  omnino 
liquidum  fiat.  Habebis  quoque 
ollam  tertiam  super  carbones 
positam,  in  qua  sit  oleum  cali- 
dum,  et  cum  gummi  penitus 
liquidum  fuerit,  ita  ut  extreme 
ferro  quasi  filum  trahitur,  in- 
funde  ei  oleum  calidum,  et  ferro 
commove,  et  insimul  coque  ut 
non  bulliat,  et  interdum  extrahe 
ferrum  et  lini  modice  super  lig- 
num sive  super  lapidem,  ut 
probes  diversitatem  ejus;  et 
hoc  caveas  in  pondere  ut  sint 
duae  partes  olei  et  tertia  gummi. 


which,  when  you  have  placed 
over  the  coals,  cook  carefully  so 
that  it  may  not  boil,  until  a  third 
part  is  evaporated;  and  guard 
from  the  winds  because  it  is  dan- 
gerous to  a  high  degree  and  diffi- 
cult to  extinguish  if  it  takes  fire 
from  the  top.  Every  picture 
smeared  over  with  this  glaze  be- 
comes clear  and  beautiful  and  in 
every  way  durable.  Set  up  four 
or  three  stones  which  are  able  to 
stand  the  fire  so  that  they  lean 
apart ;  on  these  place  a  common 
pipkin,  and  in  this  put  the  above- 
mentioned  portion  of  the  gum 
fornis,  which  is  called  Roman 
glassa  (amber),  and  over  the 
mouth  of  this  pot  set  a  smaller 
pipkin  which  has  in  the  bottom 
a  middling-sized  hole.  And 
around  these  put  luting  so  that 
nothing  may  get  out  of  the  crev- 
ice between  these  pots.  You 
should  have,  moreover,  a  slender 
iron  rod  set  in  a  handle  with 
which  you  may  stir  this  mass  of 
gum,  with  which  you  may  feel 
that  it  is  entirely  liquid.  You 
must  have  also  a  third  pot  set 
over  the  coals,  in  which  is  hot  oil, 
and  when  the  interior  of  the  gum 
has  become  liquid,  so  that  with 
the  end  of  the  iron  rod  it  may  be 
drawn  out  like  a  thread,  pour 
into  it  the  hot  oil  and  stir  it  with 


TECHNOLOGY  OF  PAINT  AND    VARNISH. 


Cumque  ad  libitum  tuum  cox- 
eris  diligenter,  ab  igne  removens 
€t  discoperiens,  refrigerari  sine. 


the  iron  rod,  and  at  the  same  time 
cook  it  so  that  it  may  not  boil, 
and  from  time  to  time  draw  out 
the  rod  and  smear  it  properly 
over  a  piece  of  wood  or  stone, 
that  you  may  find  out  if  there  is 
separation;  and  see  to  this  that 
in  weight  there  be  two  parts  of 
oil  and  the  third  of  gum.  And 
when,  in  your  judgment,  you 
have  cooked  it  thoroughly,  re- 
moving it  from  the  fire  and  un- 
covering it,  cool  it  out  of  doors. 


In  regard  to  the  resin  mentioned  in  this  by  the  name  of  "  glassa" 
it  is  proper  to  observe  that  Tacitus  (De  Moribus  Germanorum, 
c.  xlv)  and  Pliny  (1.  xxxvii,  c.  ii)  both  say  this  was  the  ancient 
German  name  for  amber.  It  will  be  observed  that  nothing  is 
said  in  the  foregoing  about  thinning  the  varnish  with  spirits  of 
turpentine.  The  "varnish  would  contain  28  gallons  (U.  S.)  of  oil 
to  100  pounds  of  resin.  It  was  to  be  warmed  and  smeared  over 
the  picture,  using  the  fingers  rather  than  a  brush  for  this  purpose. 
This  practice  was  no  doubt  of  great  antiquity.  It  was  the  com- 
mon practice  in  the  time  of  Cennini,  who  said:  "Place  the  picture 
level  and  with  your  hand  spread  the  varnish  well  over  the  surface. 
If  you  do  not  choose  to  spread  the  varnish  with  your  hand,  dip  a 
piece  of  clean  sponge  into  the  varnish  and  spread  it  over  the  pic- 
ture in  the  usual  manner"  (ch.  155). 

Formula  from  Alcherius,  1350. — Another  old  varnish  for- 
mula is  from  Alcherius,  who  gives,  under  date  of  1398,  the  follow- 
ing recipe,  which  was  communicated  to  him  by  Anthonio  de 
Compendio,  then  an  old  man,  as  an  old  and  well-known  formula : 
"To  make  a  good  liquid  varnish  for  painters:  Take  aromatic 
glassa,  which  is  dark  and  dull  outside  and  inside  when  broken  is 
clear  and  shining,  like  glass.  Put  some  of  it  into  a  new  jar,  on 
the  mouth  of  which  must  stand  another  jar,  which  must  be  well 


EARLY  HISTORY.  1 5 

luted  to  it.  The  upper  jar  must  be  well  covered  so  as  to  be  smoke- 
proof  and  its  bottom  must  be  pierced.  Then  light  a  fire  beneath 
it  and  leave  it  until  the  glassa  is  melted,  when  you  must  take  two 
parts  of  linseed-  or  hempseed-  or  nut-oil,  and  heat  this  oil  slowly 
over  a  fire,  not  making  it  too  hot.  You  must  then  pour  it  on  the 
said  glassa,  make  the  fire  hotter,  and  let  it  boil  for  an  hour,  taking 
care  that  the  flame  does  not  touch  it.  Then  take  it  off  the  fire  and 
put  it  into  a  clean  vessel,  and  when  you  wish  to  varnish  any  dry 
painting  take  some  of  this  liquid  and  spread  it  over  the  painting 
with  your  fingers,  for  if  you  were  to  do  it  with  a  pencil,  it  would 
be  too  thick  and  would  not  dry.  You  will  thus  have  good  var- 
nish." 

Formulae  from  Jacobus  de  Tholeto,  1440. — About  the  same 
date  are  the  following  by  Magister  Jacobus  de  Tholeto,  from  the 
Bolognese  MS.  from  the  convent  of  S.  Salvatore  in  Bologna, 
first  half  of  the  fifteenth  century : 

"S.  206.  To  make  liquid  varnish:  Take  of  the  gum  of  the 
juniper  (sandarac)  two  parts,  and  one  part  of  linseed-oil.  Boil 
them  together  over  a  slow  fire,  and  if  the  varnish  appears  too  stiff, 
add  more  of  the  oil  and  take  care  not  to  let  it  take  fire,  because 
you  would  not  be  able  to  extinguish  it,  and  even  if  you  would 
extinguish  it  the  varnish  would  be  dark  and  unsightly.  Let  it 
boil  half  an  hour  and  it  will  be  done." 

"S.  207.  To  make  liquid  varnish  in  another  manner:  Take 
one  pound  of  linseed-oil  and  put  it  into  a  new  glazed  jar,  and  then 
take  half  a  quarter  of  an  ounce  of  roche  alum  in  powder  and  an 
equal  quantity  of  minium  or  vermilion  ground  fine,  and  half 
an  ounce  of  incense,  also  ground  fine.  Mix  all  these  ingredients 
together  and  put  them  into  the  oil  to  boil,  stirring  it  with  a  stick, 
and  when  the  oilis  boiling,  as  it  is  likely  to  run  over,  have  another 
glazed  jar  ready  and  put  it  by  that  which  contains  the  oil,  so  as 
to  catch  the  oil  which  runs  over,  in  order  that  it  may  not  run  on 
the  ground ;  and  in  this  manner  make  it  boil  up  three  or  four  times, 
and  each  time  pour  back  what  has  run  over  on  that  which  is  boil- 
ing in  the  jar.  Having  done  this,  set  fire  to  the  oil  on  the  right- 
hand  side  with  a  lighted  straw  and  let  the  oil  burn  on  the  upper 


1 6  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

part;  so  that  the  jar  may  not  burn  on  the  inside,  on  account  of 
the  too  great  heat,  for  otherwise  the  oil  would  smell  unpleasant. 
When  you  light  the  oil  with  the  straw,  remove  the  jar  from  the 
fire,  and  let  it  burn  while  you  can  say  three  paternosters,  then 
extinguish  the  oil  with  a  wooden  cover,  putting  it  upon  the  jar, 
and  when  it  is  extinguished  remove  the  cover  in  order  to  let  the 
vapor  escape,  then  put  it  back  over  the  fire.  Do  this  three  times 
and  it  is  done." 

Formulae  from  the  Marcian  MS.,  1520. — A  hundred  years 
later,  in  the  first  part  of  the  sixteenth  century,  we  find  in  a  MS. 
of  the  library  of  San  Marco  in  Venice  the  following : 

"S.  402.  A  most  excellent,  clear,  and  drying  varnish  proper 
for  colors,  both  in  oil-painting  and  the  other  kinds  of  painting: 
Take  two  ounces  of  clear  and  good  nut-oil,  one  ounce  of  clear  and 
good  Greek  pitch  (colophony),  and  half  an  ounce  of  clear  and 
good  mastic.  Grind  the  pitch  and  the  mastic  (separately)  to  a 
very  fine  powder,  and  place  the  oil  in  a  clean  glazed  pipkin  over 
a  charcoal  fire  and  let  it  boil  gently  until  it  is  done  sufficiently, 
i.e.,  until  one-third  has  evaporated.  Then  put  in  the  powdered 
pitch,  a  little  at  a  time,  mixing  and  incorporating  it  well.  After- 
ward throw  in  the  mastic  in  the  same  manner,  and  when  it  is 
dissolved  take  the  varnish  off  the  fire  and  strain  it  through  a  fine 
and  old  linen  cloth." 

"S.  404.  A  most  excellent  varnish  for  varnishing  arquebuses, 
crossbows,  and  iron  armor:  Take  of  linseed-oil  two  pounds,  san- 
darac  one  pound,  Greek  pitch  two  ounces.  Boil  the  oil,  then  dis- 
solve in  it  the  other  ingredients  and  strain  through  a  much- worn 
linen  cloth,  and  when  you  wish  to  use  the  varnish  scrape  and 
polish  the  work  and  heat  it  in  a  hot  oven,  because  that  is  the  best 
place  to  heat  it,  and  when  it  is  at  a  proper  heat,  i.e.,  when  the  var- 
nish adheres  to  it  firmly  and  does  not  blister  from  too  great  heat, 
then  lay  it  on  thinly  with  an  instrument  of  wood,  so  that  you  may 
not  burn  your  fingers,  and  it  will  make  a  beautiful  changing  color. 

"And  if  you  supplied  the  place  of  Greek  pitch  with  naval  pitch, 
I  think  it  would  make  the  work  black  when  you  varnished  it. 

"When  making  the  varnish,  you  must  boil  it  well,  even  to  such 


EARLY  HISTORY.  17 

a  degree  as  to  make  it  foam  and  bubble,  if  necessary,  in  order  that 
it  may  be  clear  and  thick." 

"S.  405.  An  excellent  common  varnish,  good  for  varnishing 
whatever  you  please :  Take  two  ounces  of  clear  and  good  linseed- 
oil  and  one  ounce  of  clear  and  good  Greek  pitch;  but  two  ounces 
of  the  latter  will  also  make  the  varnish  thicker  and  give  it  more 
body.  Boil  the  oil  over  a  slow  fire  and  then  put  in  the  pounded 
pitch  a  little  at  a  time,  that  it  may  incorporate  well,  and  add  a 
little  roche  alum  previously  burnt  and  powdered,  and  when  it  is 
incorporated  and  boiled  sufficiently,  i.e.,  when  you  try  a  little  of 
it  in  your  fingers  and  find  that  it  is  done,  strain  it  and  keep  it. 
When  it  is  used  it  will  be  beautiful  and  good,  and  if  it  is  too  tena- 
cious you  will  dilute  it  with  a  little  oil.  And  if  you  wish  it  com- 
moner; so  as  to  sell  it  at  a  larger  profit,  take  ten  ounces  of  oil  to 
one  of  pitch;  and  if  you  use  black  pitch,  it  will  be  good  for  pom- 
mels of  swords,  spurs,  and  similar  things." 

The  following  is  also  from  the  MS.  of  San  Marco:  "Item — a 
varnish.  Take  one  pound  of  linseed-oil,  boiled  in  the  usual  way, 
and  anoint  the  vessel  with  it  while  hot,  and  four  ounces  of  pow- 
dered amber.  Place  it  to  dissolve  with  the  bottle  closed  on  the 
coals,  and  when  it  is  nearly  dissolved  pour  in  the  hot  oil  and  stop 
it  up.  Afterward,  at  the  proper  time,  when  the  whole  is  dissolved, 
stir  in  three  ounces  of  alum.  Dilute  the  varnish  with  the  neces- 
sary quantity  of  naphtha,  or  linseed-oil,  or  spirit  of  wine,  and  use 
it  warm.  .  .  . 

"Take  one  ounce  of  sandarac,  ground  to  a  very  fine  powder, 
and  three  ounces  of  clear  nut-oil.  Heat  the  oil  in  a  glazed  pipkin 
over  a  slow  fire  in  the  same  manner  as  linseed-oil  is  boiled.  Then 
add  the  powdered  sandarac,  a  little  at  a  time,  until  it  is  dissolved. 
Add  to  it  also  at  the  same  time  as  much  clear  incense  finely  pow- 
dered as  will  impart  a  pleasant  savor  to  the  whole  mixture,  stirring 
it  well  that  it  may  dissolve ;  and  if  you  please,  you  may  add  also  a 
sufficient  quantity  of  burnt  and  powdered  alum  to  have  a  sensible 
effect  on  the  whole  composition,  and  the  addition  of  the  alum  will 
improve  the  varnish,  if  you  stir  it  until  it  is  dissolved.  It  should 
then  be  strained  through  a  linen  cloth  and  afterward  exposed  to 


1 8  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

the  sun  and  dew  until  a  sediment  is  formed,  which  should  be 
separated  by  pouring  off  the  clear  varnish,  after  which  it  will  be 
ready  for  use." 

Formulae  from  Rossello,  1575. — The  following  are  from  the 
Secreti  of  Timotheo  Rossello,  Venice,  1575:  "To  make  liquid 
varnish:  Take  one  pound  of  sandarac  resin  and  four  pounds  of 
linseed-oil.  Place  the  oil  on  the  fire  to  boil;  take  another  vessel 
for  the  resin,  adding  three  ounces  of  oil,  little  by  little;  stir  con- 
tinually with  a  spatula  and  let  the  oil  continue  to  boil  till  the 
whole  is  transferred  to  the  vessel  containing  the  varnish.  Keep 
up  a  good  fire  for  the  said  varnish  and  in  order  to  know  when  the 
mixture  has  been  boiled  enough,  and  if  it  remains  thick  and  some- 
what firm  the  varnish  is  made.  Then  remove  it  from  the  fire  and 
strain  through  a  cloth. 

"To  make  a  superior  liquid  varnish:  Take  three  pounds  of 
yellow  amber  and  six  ounces  of  pulverized  brick.  Make  a  fur- 
nace with  two  orifices  below,  each  orifice  having  bellows  adapted 
to  it.  The  fire,  which  should  be  of  charcoal,  requires  to  be  great. 
Let  there  be  an  opening  above;  in  this  fit  a  glazed  vessel  which 
is  to  be  luted  to  the  opening  so  that  the  fire  may  not  penetrate, 
for  if  it  were  to  do  so  the  ingredients  would  presently  be  in  a 
flame.  Place  your  amber  in  the  vessel  with  as  much  of  the  oil  as 
will  cover  it,  then  blow  with  a  bellows  and  make  a  great  fire  till 
the  amber  dissolves.  As  there  is  great  danger  of  fire,  have  a 
wooden  trencher  ready,  wrapped  round  with  a  wet  cloth,  and  if 
the  varnish  should  catch  fire  cover  the  vessel  with  the  trencher. 
Meanwhile  boil  in  another  vessel  the  remainder  of  the  oil,  mak- 
ing a  moderate  fire  with  the  charcoal,  but  still  taking  care  that  the 
flame  does  not  ascend.  Let  this  oil  continue  to  boil  till  it  be  re- 
duced one-third.  Then  when  the  amber  is  dissolved  in  the  small 
quantity  of  oil  first  mixed  with  it,  as  above  described,  throw  in  the 
remaining  oil  which  you  have  heated  to  ebullition,  and  mix 
together  for  the  space  of  five  minutes,  so  as  to  incorporate  all 
well.  Then  remove  from  the  fire  and  throw  in  the  pulverized 
brick  above  mentioned.  Stir  again  a  little,  then  cover  the  vessel, 
let  the  contents  settle,  and  the  varnish  is  made." 


EARLY  HISTORY.  *9 

Mathioli,  1549. — Mathioli  in  1549  said:  "The  juniper  pro- 
duces a  resin  similar  to  mastic,  called  (though  improperly)  san- 
darac.  This,  when  fresh,  is  light  in  color  and  transparent,  but 
as  it  acquires  age  it  becomes  red.  With  this  resin  and  linseed- 
oil  is  prepared  the  liquid  vernix  which  is  used  for  giving  lustre 
to  pictures  and  for  varnishing  iron." 

Formula  from  Libravius,  1599. — Libravius,  in  his  Singularia, 
in  1599-1601,  says:  "Take  three  pounds  of  linseed-oil;  of  burnt 
alum,  purified  turpentine,  and  garlic,  each  half  an  ounce.  Mix 
these  in  the  oil  and  boil  till  it  ceases  to  froth.  Then  take  one 
pound  of  amber  (succinum),  place  it  in  a  vessel,  the  cover  of 
which  has  an  opening  about  the  size  of  the  little  finger.  Pour  in 
a  little  oil.  Melt  the  amber  on  a  tripod  and  stir  it  with  an  iron 
rod  inserted  through  the  opening  in  the  cover,  to  assist  the  lique- 
faction. When  dissolved,  mix  with 'the  oil  before  prepared  and 
boil  to  the  consistence  of  a  varnish." 

Caneparius,  1619. — The  following  is  by  Caneparius  (Venice, 
1619): 

"The  sandarac  of  the  Arabs  is  called  Dry  Vernix.  From 
this  and  linseed-oil  is  made  the  dark  liquid  vernix  so  well 
adapted  for  giving  lustre  to  pictures  and  statues.  It  even  adds 
splendor  to  iron  and  preserves  it  from  rust." 

Formula  from  Albert!,  1750. — Alberti  (Magdeburg  1750), 
writing  on  amber,  says:  "Dissolve  one  pound  of  pulverized 
amber  in  an  earthen  vessel,  on  a  charcoal  fire.  As  soon  as  it 
is  melted  pour  it  on  an  iron  plate  and  again  reduce  it  to  powder. 
Then  place  it  in  an  earthen  vessel,  first  adding  linseed-oil  already 
boiled  and  prepared  with  litharge.  The  solution  is  completed 
by  the  addition  of  spirits  of  turpentine." 

The  foregoing  formulae,  which  are  selected  from  a  great 
number  known  to  the  writer,  give  a  fair  idea  of  the  knowledge 
of  the  art  of  varnish-making  in  the  middle  ages.  The  con- 
clusion I  have  reached  from  a  careful  study  of  the  whole  subject, 
as  far  as  the  records  are  accessible  to  me,  is  that  the  best  varnish 
was  made  from  amber,  or  rather  from  what  was  called  amber, 


20  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

the  term  being  made,  as  the1  records  show  (but  which  are  not 
included  here  on  account  of  lack  of  space),  to  include  certain 
hard  varnish  resins  from  the  East.  This  varnish  was  made 
originally  without  spirits  of  turpentine  or  any  other  thinner, 
and  in  order  to  have  it  sufficiently  liquid  it  was  made  with  a 
large  amount  of  oil,  from  twenty-five  to  fifty  gallons  of  oil  to 
the  hundred  pounds  of  resin  (to  put  it  in  the  terms  of  modern 
varnishes),  well  cooked  and  slow-drying.  The  oil  was  carefully 
refined,  as  will  be  described  later,  and  probably  was  made  dry- 
ing with  litharge  and  possibly  with  umber,  but  the  painter 
expected  to  allow  a  long  time  for  his  work  to  dry,  in  some  cases 
a  year  or  more  for  the  paint  to  dry  before  the  final  varnishing; 
and  if  haste  was  necessary,  the  use  of  an  oven  or  other  source 
of  heat  was  the  alternative.  There  was  practically  no  progress 
for  eight  hundred  years,  the  varnish  made  by  Theophilus  being 
quite  equal  to  that  made  in  the  eighteenth  century,  and  when 
a  really  good  varnish  was  desired  recourse  was  had  to  this  old 
formula,  which  was  handed  down  from  one  generation  of  artisans 
to  another.  There  were  no  varnish-makers  in  the  modern 
sense  until  the  nineteenth  century,  i.e.,  no  established  business 
of  varnish-making,  but  every  important  manufacturing  estab- 
lishment had  its  own  varnish-maker,  who  made  up  small  quan- 
tities, but  the  more  important  apothecaries  in  the  large  cities 
sold,  and  in  some  cases  made,  varnish;  sometimes  "common 
liquid  varnish"  only,  which  was  made  with  sandarac  or  other 
cheaper  resin;  sometimes  this  and  also  amber  varnish.  But 
always  small  batches  were  made.  Near  the  end  of  the  eighteenth 
century  Tingry,  the  most  noted  varnish-maker  of  his  time,  warns 
his  followers  that  six  ounces  of  amber  is  as  large  a  melt  as  is 
advisable.  It  will  further  be  shown  that  varnish  was  known 
before  the  Christian  era,  and  there  can  be  no  reasonable  doubt 
that  knowledge  of  the  art  was  continuous  from  at  least  as  early 
as  500  B.C.,  when  those  varnishes  were  made  which  still  exist 
on  the  Egyptian  mummy-cases  already  mentioned,  down  to 
the  present  time,  and  it  seems  likely  that  the  formula  of  Theophilus 
may  have  been  handed  down  from  those  early  Egyptian  work- 


EARLY  HISTORY.  21 

men.  This  latter  conclusion  may  strike  the  reader  as  an  unsup- 
ported conjecture;  and  since  the  matter  is  one  of  interest  to  all 
those  who  care  to  know  about  the  origin  of  the  art,  it  is  worth 
while  to  give  some  of  the  grounds  which  seem  to  support  such 
a  proposition. 

Varnish-making  Probably  Continuous  from  Egyptian  Times. 
— In  the  first  place,  nothing  is  so  conservative  as  tradition  in 
artisanship.  We  still  wear  the  buttons  on  our  coat-sleeves  which 
were  used  by  our  ancestors  in  the  dark  ages  to  fasten  back  their 
sleeves  when  they  went  into  battle,  and  those  on  the  backs  of 
our  coats  with  which  they  buttoned  up  their  skirts  to  ride  in 
the  saddle.  Hundreds  of  such  instances  are  known  to  the 
student.  Those  who  have  not  studied  such  things  cannot 
imagine  how  persistent  habits  and  methods  of  workmanship 
are.  The  fact  that  the  process  of  Theophilus  which  he  put 
down  as  the  old  and  approved  one,  continued  for  hundreds  of 
years  after  his  time  and  is  still  almost  exactly  practised,  only 
with  some  additions  and  on  a  larger  scale,  a  thousand  years 
after  it  was  known  to  the  men  who  communicated  it  to  him, 
is  in  reality  a  substantial  reason  for  believing  that  it  had  then 
existed  a  long  time.  This  is  also  strongly  supported  by  the 
appearance  of  the  Egyptian  varnish.  Too  much  stress  cannot 
be  laid  on  the  fact  that  here  we  are  not  dealing  with  tradition 
or  history,  but  with  the  real  and  actual  thing.  Here  is  the  var- 
nish, just  as  it  was  applied  twenty-five  hundred  years  ago.  It 
is  just  as  real  as  the  mummy  itself,  and  is  just  as  absolute  a  proof 
that  varnish  was  made  in  those  days  as  the  mummy  is  proof 
that  people  lived  in  those  days.  Here,  I  say,  is  the  actual  and 
real  varnish.  It  was  made  with  resin  and  oil.  It  was  smeared 
on,  possibly  with  a  spatula,  but  more  likely  with  the  fingers, 
certainly  not  put  on  with  a  brush  nor  in  a  thinly  fluid  condition. 
Such  a  varnish  as  Theophilus  describes  would  look  as  that  looks, 
and  in  all  probability  would  last  as  that  has  endured. 

Materials  Known  to  the  Egyptians. — To  the  question  as  to 
whether  the  Egyptians  knew  of  the  materials  we  can  say  that 
obviously  they  had  suitable  materials  and  that  there  is  no  reason 


22  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

why  they  may  not  have  been  the  same.  As  to  resins,  we  know 
that  for  thousands  of  years  the  Egyptians  had  made  warlike 
incursions  into  tropical  Africa,  whence  come  our  best  varnish- 
resins,  and  it  is  extremely  probable  that  some  commerce  existed 
between  those  regions  and  Egypt;  also  that  no  resins  native  to 
northern  Africa  or  Arabia  are  known  to  be  as  durable  as  these 
varnishes  have  shown  themselves  to  be.  The  Chinese  have 
from  very  ancient  times  imported  varnish-resins  from  the  East 
Indies  which  shows  that  resins  are  naturally  objects  of  commerce, 
and  the  Egyptians  were  probably  equally  enterprising  traders. 
It  is  very  curious  that  they  did  not  dilute  their  varnish  with 
essential  oil  of  turpentine,  for  this  was  really  the  substance  known 
to  Herodotus  and  later  writers  as  "oil  of  cedar,"  which  they 
used  in  considerable  quantities  for  embalming  purposes.  It  is 
equally  singular  that  this  was  not  practised  by  Theophilus,  nor 
for  three  or  four  hundred  years  after  his  time,  but  such  is  the 
undoubted  fact,  and  it  bears  out  the  hypothesis  that  the  formula, 
perhaps  of  immeasurable  antiquity,  had  been  found  to  give 
satisfactory  results  and  no  modification  of  it  was  allowed.  We 
do  not  know  that  the  Egyptians  used  linseed-oil,  or  knew  it, 
but  we  do  know  that  they  used  linen  and  cultivated  the  flax-plant 
and  therefore  saved  and  stored  linseed.  We  also  know  that 
they  knew  and  used  olive-oil,  which  is  of  remote  antiquity,  and 
hence  must  have  had  oil-presses.  We  also  know  that  linseed- 
oil  was  in  early  times  extracted  with  an  olive-oil  press,  for 
Theophilus  gives  the  following  directions: 

Formula  from  Theophilus  for  Making  Linseed-oil. — "Take 
linseed  and  dry  it  in  a  pan,  without  water,  on  the  fire.  Put 
it  in  a  mortar  and  pound  it  to  a  fine  powder.  Then,  replacing 
it  in  a  pan  and  pouring  water  on  it,  make  it  quite  hot.  After- 
ward wrap  it  in  a  piece  of  new  linen;  place  it  in  a  press  used 
for  extracting  the  oil  of  olives,  or  of  walnuts,  or  of  the  poppy, 
and  express  this  in  the  same  manner." 

If  the  Egyptians  had  for  thousands  of  years  been  familiar 
with  linseed  and  with  the  oil-press  (as  they  were),  it  is  not 
unlikely  that  they  had  put  the  two  together.  Pliny,  who  wrote 


EARLY  HISTORY.  23 

about  the  beginning  of  the  Christian  era,  says  (1.  xiv,  c.  25): 
"Resina  omnis  dissolvitur  oleo" — oil  dissolves  all  resins.  Dios- 
corides,  who  was  before  Pliny,  describes  walnut-  and  poppy-oils. 
Hippocrates,  who  lived  in  the  fifth  century  B.C.,  recommends 
linseed  poultice.  Galen,  who  lived  in  the  second  century  A.D., 
says  that  linseed  is  in  its  nature  drying.  Walnut-  and  poppy- 
oils  are  also  drying  oils,  and  one  of  these  may  have  been  used, 
but  there  is  no  reason  to  think  that  they  were  used  before  linseed, 
except  that  they  are  better  suited,  especially  walnut-oil,  to  be 
used  for  food.  Fresh  walnut-oil  is  nearly  as  good  as  olive-oil, 
but  it  is  to  be  remembered  that  at  the  present  day  in  Russia 
linseed-oil  is  used  as  food. 

Use  of  Varnish  by  Apelles. — Apelles,  who  lived  in  the  fourth 
century  B.C.,  was  the  court-painter  of  Alexander  the  Great. 
Pliny  (1.  xxxv,  c.  18)  says  of  him:  "No  one  was  able  to  imitate 
one  thing,  in  that  he  spread  the  varnish  over  his  completed  work 
so  thin  that  it  brought  out  the  brilliancy  of  the  colors  by  reflection 
and  protected  it  from  dust  and  dirt."  Also  Cicero  (ad  Divers, 
1.  9,  §  36)  says:  "Apelles  finished  the  head  of  Venus  with  the 
highest  polish."  The  picture  of  Venus  was  one  of  his  most 
celebrated  works.  Praxiteles  was  a  Greek  sculptor  who  lived 
in  the  fourth  century  B.C.  and  who  employed  Nicias,  a  painter, 
to  tint  and  varnish  his  statues. 

By  Nicias. — In  book  xxxv,  ch.  28,  Pliny  says:  "It  is  Nicias 
of  whom  Praxiteles,  being  asked  which  of  his  marble  statues  he 
most  valued,  answered,  those  to  which  Nicias  had  put  his  hand; 
so  much  care  he  had  taken  in  rubbing  them."  The  word  here 
translated  "rubbing"  (circumlitioni)  has  the  peculiar  meaning 
of  smearing  on  with  a  rubbing  motion,  and  the  passage  indicates 
that  the  varnish  was  applied  with  the  hand  and  polished  by 
rubbing,  in  the  way  described  1400  years  later  by  Theophilus. 
Protogenes  was  another  Grecian  painter,  whose  picture  of 
Jalysus  was  his  most  celebrated  work,  and  it  appears  from  the 
following  passage  from  Cicero  that,  like  Apelles,  he  polished 
his  paintings:  "And  as  I  believe  Apelles  and  Protogenes  saw 
with  grief,  the  one  his  Venus,  the  other  his  Jalysus,  covered 


24  TECHNOLOGY  OF   PAINT  AND    VARNISH. 

with  dirt;  so  I  cannot  without  extreme  distress  see  so  strangely 
disfigured  a  man  whom  I  have  painted  and  polished  with  all 
the  colors  of  art."  (Cic.  ad.  Att,  lib.  2,  Epist.  21.)  This  pas- 
sage may  have  suggested  the  following  to  Lord  Bacon:  "The 
fame  of  Cicero  had  not  borne  her  age  so  well,  if  it  had  not  been 
joined  with  some  vanity.  Like  unto  varnish,  which  makes 
ceilings  not  only  shine,  but  last." 

Poetical  References  to  Varnish  by  Leonidas.  —  In  the  early 
part  of  the  third  century  B.C.  there  was  a  Greek  poet  named 
Leonidas,  who  is  best  known  by  dedicatory  verses  and  inscrip- 
tions on  works  of  art.  One  of  these  short  poems,  on  a  picture 
of  Eros  —  is  here  given: 


rov  "Epwra  rls 
x^S'duroO  Z-rjvbs 
?ro5'  fH0a/0"r<p  /cetrcu  <TK07r6s,  bv  Ka6op8.<r0ai 
irvpl  rv\f/6fJLevov. 
Anthol.  Grec.,  Epig.  lib.  I,  cap.  xxvi. 


Translation: 


"Who  has  polished  with  the  resin  of  incense  this  Eros  armed  with  arrows,  who 

does  not  respect  Zeus  himself? 

At  last  behold  him  placed  as  a  mark  for  Hephaistos,  seen  to  be  consumed  by 
fire." 

Another  somewhat  similar  passage,  also  an  inscription  on  a 
painting,  shows  in  like  manner  that  varnish  was  either  the 
medium  or  the  characteristic  surface  of  the  picture: 


MiJ  /J.e  rbv  £K  \i^dyoiO  \4j€^ve,  rov 
Te/>7r6/ie»'OJ'  wxioi;   rfidtuv  odpois, 

Bcuos  £y<j)  vij'/Ji^'Yjs  airb  yeirovos  a 
"M.OVVOV  eirorptivw  e/rya 

"EvOev  dr'   tvKdpirov  pe  <j>L\i)S  eSe^av 


A  translation  of  the  beginning  of  this  is  as  follows  and  is  addressed 
to  the  painter: 

"  Friend,  no  more  remind  me  with  resin  of  incense  (i.e.,  varnish)  how  a  depraved 
youth  passed  the  time  in  riotous  orgies,"  etc., 


EARLY  HISTORY.  25 

and  goes  on  to  tell  how  he  has  adopted  good  habits,  etc.  The 
remainder  of  the  poem  indeed  is  like  an  order  for  another  picture, 
showing  the  youth  in  good  company,  laboring  in  his  orchard, 
interested  in  the  changing  seasons. 

Still  another  Greek  verse,  on  the  picture  of  a  maiden,  with 
the  same  reference  to  the  use  of  varnish: 


Xi/Sdpou,   Xaotrwv  5e/xas, 
,   KO.I  IIa0tT7$  virtp  \ay6vuv. 

Translation  : 

"Maiden,  thou  hast  celebrity  from  the  resin  (varnish);   to  it  them  owest  thy  form 
of  the  Graces,  thy  eloquence,  and  around  thy  waist  the  girdle  of  Venus." 

In  all  the  foregoing  the  same  word  (Xifiavov)  is  used,  which  has 
been  rendered  resin,  or  resin  of  incense.  It  is  the  word  from 
which  comes  our  word  olibanum,  which  is  the  name  of  the  resin 
of  frankincense,  but  was  used  to  denote  any  or  all  of  the  incense- 
resins,  which  were  used  for  making  the  commoner  kinds  of 
varnish.  It  appears  to  have  sometimes  been  the  custom  to 
apply  these  resins  in  the  'form  of  a  powder  which  was  then  melted 
by  holding  a  hot  iron  or  a  torch  near  them,  after  which  the  sur- 
face could  be  polished  by  rubbing.  Eastlake,  who  appears 
to  have  studied  this  subject  carefully,  thinks  that  the  pigments 
used  were  mixed  with  melted  wax  and  applied  with  a  brush. 
When  cold,  the  surface  was  remelted  to  produce  an  apparently 
enamelled  surface.  This  was  enhanced  by  mixing  resin  with 
the  wax  to  harden  it,  or  by  adding  resin  to  the  surface,  which 
formed  a  varnish.  This  was  in  the  case  of  encaustic  painting; 
distemper  painting  could  be  treated  somewhat  in  the  same 
manner,  or  varnished  in  the  ordinary  way.  It  was  evidently 
possible  to  get  in  some  such  way  an  extremely  high  lustre  on 
encaustic  (wax)  paintings,  as  is  illustrated  by  the  following 
verse  from  the  Greek  anthology: 

"Apea  Kal  Ha^irjv  6  farypd^os  £s  ptvov  dlxov 


'Ex  ftvpldos  dt  /j.o\&v  Qateuv,   iro\virdfji(paos 
^poi>s  ffKotrtuv. 
rivos;   6u5'   eVt   /cr?pou 


26  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

Translation : 

"A  painter  represents  Mars  and  Venus  in  the  middle  of  a  temple.  The  sun, 
shining  in  through  the  doorway,  scatters  rays  of  the  most  dazzling  brilliancy.  The 
painter  stands  in  astonishment  and,  looking  at  the  two,  he  wonders  if  the  sun  is 
angry,  or  wishes  to  throw  his  wrath  on  the  inanimate  wax." 

Vitruvius  on  Polishing  Varnish. — That  varnish  was  polished 
by  rubbing  is  also  indicated  by  the  following  from  Vitruvius 
(1.  vii,  c.  4):  "In  his  vero  supra  podia,  abaxi  ex  atramento  sunt 
subigendi  et  poliendi  cuneis  silaceis,  seu  miniaceis  interpositis." 
"  Among  these  panels  over  the  balcony  the  wainscoting  is  rubbed 
and  polished  with  varnish,  with  ochre  or  minium  interposed." 

The  use  of  wax  except  as  a  floor-varnish  has  almost  ceased, 
but  with  that  exception  there  is  nothing  in  all  these  passages 
which  indicates  any  change  of  importance  from  the  earliest 
times  down  to  what  we  may  call  the  historic  period  of  varnish; 
and  if  the  various  practices  of  using  varnishes  have  been  the 
same,  and  if  all  we  can  learn  of  the  composition  of  them  seems 
without  change,  it  would  seem  not  unreasonable  to  suppose  that 
the  processes  of  varnish-making  have  also  been  handed  down, 
without  important  variation,  from  at  least  the  time  when  the 
varnish  on  the  mummy-cases'  was  made,  i.e.,  about  twenty-five 
hundred  years.  The  most  likely  criticism  is  that,  as  varnishes 
made  now  do  not  last  but  a  few  years,  it  appears  that  we  have 
lost  the  art  known  to  the  ancients.  I  reply,  we  have  not  lost 
the  knowledge,  but  we  have  lost  the  patience  necessary  to  the 
use  of  the  most  permanent  and  durable  preparations.  This 
will  be  clearly  illustrated  in  a  later  chapter. 


CHAPTER   III. 

VARNISH:    ORIGIN  OF  THE  -NAME. 

IN  the  middle  of  the  third  century  B.C.  Berenice,  whose 
grandfather  was  a  half-brother  of  Alexander  the  Great,  a  very 
beautiful  golden-haired  woman,  one  of  whose  descendants  was 
the  famous  Egyptian  queen  Cleopatra,  was  Queen  of  Cyrene 
and  wife  of  Ptolemy  Euergetes,  King  of  Egypt.  Not  long  after 
her  marriage  the  king,  her  husband,  engaged  in  a  long  and 
highly  successful  campaign  in  Asia,  during  the  time  of  which 
the  queen  offered  up  prayers  for  his  successful  return,  vowing 
to  sacrifice  her  beautiful  hair  on  the  altar  of  Venus  if  the  king 
should  come  back  in  safety.  This  she  accordingly  did;  but 
the  shining  and  jewelled  tresses  disappeared  during  the  night 
from  the  altar,  and  it  was  found  by  the  astronomer  Conon  that 
the  deities  had  carried  them  to  heaven,  where  they  form,  in  the 
Milky  Way,  the  constellation  still  known  as  the  Coma  Berenices, 
or  Berenice's  Hair.  The  poet  Callimachus  celebrated  them 
in  Greek  verse  as 

"The  consecrated  spoils  of  Berenice's  golden  head"; 

and  Catullus,  telling  of  the  rivalry  between  Venus  and  Juno, 
says  that 

"The  winged  messenger  came  down 
At  her  desire,  lest  Ariadne's  crown 
Should  still  unrivalled  glitter  in  the  skies; 
And  that  thy  yellow  hair,  a  richer  prize, 
The  spoils  devoted  to  the  powers  divine, 
Might  from  the  fields  of  light  as  brightly  shine." 

When  to  the  Greeks  was  brought  from  the  far-off  shores  of 
the  unknown  Northern  Sea  the  yellow  translucent  mineral  we 

27 


28  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

know  as  amber,  they  likened  it  to  the  sacred  yellow  locks  of 
the  beautiful  Grecian  woman,  the  first  queen  in  her  own  right 
of  the  Macedonian  race,  and  called  it  by  her  name,  Berenice, 
and  by  this  name  it  was  known  both  to  the  Greeks  and  Romans 
for  several  centuries.  "Amber"  was  an  adjective  not  infre- 
quently applied  to  the  hair  of  fair  women.  The  Emperor  Nero, 
who  sometimes  affected  to  be  a  poet,  wrote  verses  to  the  amber 
hair  of  his  empress,  Poppcea;  in  consequence  of  which,  observes 
Pliny  (1.  xxxvii,  c.  12),  amber-colored  hair  became  fashionable 
in  Rome;  and  before  this  Ovid  (Metamorphoses,  1.  xv,  316) 
said,  "Electro  similes  faciunt  auroque  capillos " — "Her  hair 
was  like  amber  and  gold."  Because  of  its  beauty,  amber  has 
always  been  a  poetic  simile.  An  ancient  Persian  poet  says: 

"  But  clear  as  amber,  fine  as  musk, 

Is  Love  to  those  who,  pilgrim-wise, 
Walk  hand  in  hand,  from  dawn  to  dusk, 
Each  morning  nearer  Paradise." 

The  word  Berenice  is  equivalent  to  Pheronice,  literally  meaning 
"bringing  victory."  Ph  (<£)  is  changed  to  B  in  some  Greek 
dialects,  even  in  classic  Greek,  and  B  was  in  some  dialects  pro- 
nounced like  our  V,  as  it  now  is  by  modern  Greeks,  and  as  it 
was  in  the  middle  ages.  Hence  the  word  Berenice,  meaning 
amber,  was  often  written  Verenice  in  Latin,  and  when  we  get 
down  to  the  twelfth  century  we  find  in  the  Mappae  Claviculi 
the  word  spelled  in  the  genitive  verenicis  and  vernicis.  This  is 
probably  the  earliest  instance  of  the  Latinized  word  nearly  in 
its  modern  form,  the  original  nominative  vernice  being  after- 
ward changed  to  vernix,  when  comes  our  word  varnish.  The 
German  name  for  amber  is  Bernstein,  or  Berenice's  stone,  and 
the  Spanish  word  for  varnish  is  Berniz,  nearer  to  the  Greek  than 
our  own  word,  which  comes  through  the  later  Latin.  Veronice, 
or  Verenice,  is  the  common  name  for  amber  in  the  MS.  of  the 
middle  ages.  Eustathius,  a  twelfth-century  editor  of  Homer, 
says  that  the  later  Greeks  called  Electron  (amber)  by  the  name 
of  Beronice;  and  Salmasius  writes  it  Berenice  and  Verenice.  In 
the  Lucca  MS.  (eighth  century)  Veronica  is  often  mentioned 


VARNISH:   ORIGIN  OF   THE  NAME.  29 

as  an  ingredient  of  liquid  varnish,  and  this  latter  word,  Veronica, 
is  the  modern  equivalent  of  the  name  Berenice.  Saint  Veronica, 
however,  had  nothing  to  do  with  Berenice,  but  perhaps  she 
might  be  adopted  as  a  patron  saint  by  the  varnish-makers.  Her 
sanctity  does  not  appear  to  be  of  the  highest  order,  since  the 
observance  of  her  festival  is  not  obligatory. 

Such  is  the  origin  of  the  word  varnish.  It  was  originally 
equivalent  to  amber,  and  amber  is  a  type  of  the  highest  class 
of  resins  used  in  the  art.  The  early  Greek  word  for  amber 
was  elektron,  from  the  verb  elko,  meaning  to  draw,  because 
amber  when  rubbed  becomes  electrical  and  draws  straws  and 
other  light  objects  to  itself,  whence  also  the  word  electricity. 
The  Arabic  and  Persian  term  for  amber  is  Karabe,  from  Kahruba, 
meaning  straw-stealing,  and  Buttman  states  that  the  word  Raf 
or  Rav,  meaning  to  seize,  is  the  name  for  amber  in  the  north 
of  Germany. 

Salmasius  says  that  the  word  vernix  was  misappropriated  to 
mean  sandarac,  because  of  the  resemblance  of  that  resin  to 
amber.  After  the  sixteenth  century  the  term  vernix  ceased  to- 
be  applied  exclusively  to  the  dry  resin,  and  was  used,  as  it  is 
now,  to  mean  the  liquid  compound. 

Glassa. — As  has  already  been  mentioned,  both  Tacitus  and 
Pliny  say  that  the  Germans  of  their  time  called  amber  by  the 
name  of  glessum  or  glassa,  which  is  supposed  to  be  the  original 
of  our  word  glass.  Tacitus  believed  amber  to  be  the  juice  of  a. 
tree,  because  they  find  insects  in  it.  Thus  it  is,  he  says,  that  in 
the  Orient  there  are  trees  from  which  trickle  frankincense  and 
balsam,  which  made  him  suppose  that  there  are  in  the  west  re- 
gions and  islands  where  the  sun  draws  from  certain  trees  a  sapr 
which,  falling  into  the  sea,  is  by  it  thrown  up,  hardened,  on  the 
shore. 

Copal. — Another  word  which  is  of  common  use  in  this  connec- 
tion is  copal.  This  is  a  comparatively  modern  word,  and  is  from 
the  language  of  some  of  the  aborigines  of  'Spanish  America,  con*- 
monly  said  to  be  Mexican,  and  is  said  to  signify  any  kind  of  resin 
exuding  from  trees.  The  earliest  writer  who  mentions  copal  by 


30  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

this  name  as  an  ingredient  of  varnishes  is  probably  Fra  Fortunato, 
of  Rovigo,  the  recipes  in  whose  "Secreti,"  date  from  1659  to 
1711.  The  next  author  is  Calomino,  who  gives  a  recipe  for 
varnish  composed  of  copal  dissolved  in  spirits  of  turpentine  (see 
the  Pharmaceutical  Journal,  Vol.  IV,  p.  4).  As  now  used,  copal 
is  a  generic  term,  including  about  all  the  varnish  resins  which  are 
commonly  combined  with  oil,  and  is  not  sufficiently  definite  to 
be  used  by  varnish-makers.  Copal  varnish  is  a  trade  name, 
usually  for  a  very  inferior  article  made  of  common  rosin,  or  colo- 
phony, and  containing  no  copal;  somewhat  as  the  word  "cafe" 
is  used  on  the  windows  of  grog-shops.  In  former  times  " amber" 
seems  to  have  been  used  somewhat  in  the  same  way  as  "copal" 
now  is,  but  was  restricted  to  the  hard' and  valuable  resins;  besides 
which  there  always  was  a  specific  substance  known  by  that  name, 
being  the  same  that  we  now  call  amber,  a  yellow  or  red  resin  from 
the  shores  of  the  Baltic.  Amber  has  almost  passed  out  of  use  as 
a  varnish-resin.  The  larger  pieces  are  used  for  mouthpieces  for 
pipes,  and  the  smaller  pieces  are,  it  is  said,  cemented  together  to 
make  larger  ones.  It  is  said  to  be  difficult  to  melt,  but  the  writer 
has  not  found  this  to  be  the  case.  It  does,  however,  make  a  dark 
varnish  and  appears  to  be  too  costly  to  be  much  used.  The  fact 
that  genuine  amber,  when  polished,  retains  its  surface  longer  than 
any  other  resin  may  indicate  that  the  varnish  made  from  it  is  of 
a  high  degree  of  permanence.  It  is  commonly  so  with  the  other 
resins. 


CHAPTER    TV! 

LINSEED-OIL. 

VEGETABLE  OILS  have,  from  the  earliest  times,  been  extracted 
from  the  oil-bearing  substance  by  the  aid  of  a  press ;  but  while  this 
is  the  most  economical  and  efficient  way,  as  shown  by  the  fact 
that  it  is  the  modern  method,  it  is  not  the  only  one.  To  get  an 
idea  of  the  way  processes  and  practice  were  handed  down,  and 
how  independent  artists  and  artisans  were  of  manufactured  prod- 
ucts, each  producing  for  himself  all  that  he  needed,  thereby  being 
sure  of  its  quality,  it  may  be  well  to  see  what  was  the  manner  of 
apprenticeship  prescribed  by  Cennini,  who  wrote  the  first  treatise 
on  painting  which  has  come  down  to  us,  and  which  describes  his 
own  experience  in  the  fourteenth  century: 

"Know  that  you  cannot  learn  to  paint  in  less  time  than  that 
which  I  shall  name  to  you.  In  the  first  place,  you  must  study 
drawing  for  at  least  one  year;  then  you  must  remain  with  a  mas- 
ter at  the  workshop  for  the  space  of  six  years  at  least,  that  you 
may  learn  all  the  parts  and  members  of  the  art — to  grind  colors, 
to  boil  down  glues,  to  grind  plaster,  to  acquire  the  practise  of 
laying  grounds  on  pictures,  to  work  in  relief,  and  to  scrape  or 
smooth  the  surface,  and  to  gild;  afterwards,  to  practise  coloring, 
to  adorn  with  mordants,  paint  cloths  of  gold,  and  paint  on  walls, 
for  six  years  more — drawing  without  intermission  on  holydays  and 
workdays.  And  by  this  means  you  will  acquire  great  experience. 
If  you  do  otherwise,  you  will  never  attain  perfection.  There  are 
many  who  say  that  you  may  learn  the  art  without  the  assistance 
of  a  master.  Do  not  believe  them;  let  this  book  be  an  example 
to  you,  studying  it  day  and  night.  And  if  you  do  not  study  under 

31 


3 2  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

some  master,  you  will  never  be  fit  for  anything,  nor  will  you  be 
able  to  show  your  face  among  the  masters." 

Bearing  in  mind  the  foregoing,  it  is  interesting  to  see  how  oil 
was  prepared  in  the  laboratory  of  Leonardo  da  Vinci,  the  greatest 
painter  of  his  time,  in  the  fifteenth  and  sixteenth  centuries.  The 
recipe  was  found  in  his  own  handwriting  and  describes  the  process 
of  making  oil  of  walnuts,  which,  on  account  of  its  pale  color,  has 
always  been  a  favorite  with  artists. 

Oil-extraction  in  the  Fifteenth  Century. — "The  nuts  are  cov- 
ered with  a  sort  of  husk  or  skin,  which  if  you  do  not  remove  when 
you  make  the  oil,  the  coloring  matter  of  the  husk  or  skin  will  rise 
to  the  surface  of  your  painting  and  cause  it  to  change.  Select  the 
finest  nuts,  take  off  the  shells,  put  them  into  a  glass  vessel  of  clean 
water  to  soften  until  you  can  remove  the  skin,  change  the  water, 
and  put  the  nuts  into  fresh  water  seven  or  eight  times,  until  it 
ceases  to  be  turbid.  After  some  time  the  nuts  will  dissolve  and 
become  almost  like  milk.  Put  them  then  into  a  shallow  open  vessel 
in  the  ah*  and  you  will  soon  see  the  oil  rise  to  the  surface.  To 
remove  it  in  a  pure  and  clean  state,  take  pieces  of  cotton,  like  v 
those  used  for  the  wicks  of  lamps ;  let  one  end  rest  in  the  oil  and 
the  other  drop  into  a  vase  or  bottle,  which  is  to  be  placed  about 
the  width  of  two  fingers  below  the  dish  containing  the  oil.  By 
degrees  the  oil  will  filter  itself,  and  will  drop  quite  clear  and 
limpid  into  the  bottle,  and  the  lees  will  remain  behind.  All  oils 
are  of  themselves  quite  limpid,  but  they  change  color  from  the 
manner  in  which  they  are  extracted." 

The  foregoing  is  a  good  illustration  of  the  manner  in  which 
oils  are  extracted  by  water  without  pressure.  It  is  to  be  remem- 
bered that  in  the  most  modern  practice  of  oil-pressing  it  is  cus- 
tomary to  moisten  the  ground  seed  with  water  or  steam,  showing 
that  water  seems  necessary  to  start  the  separation  of  the  oil  from 
the  solid  part  of  the  seed,  probably  by  swelling  and  softening  the 
tissues  so  that  the  oil  can  escape.  In  the  multitudinous  recipes 
of  the  middle  ages  there  are  many  which  show  how  universal  was 
the  belief,  or  knowledge,  that  water  was  essential  to  the  separation 
or  purification  of  oil.  The  most  common  method  of  purifying 


LINSEED-OIL.  33 

linseed-oil  consisted  in  mixing  the  oil  in  a  large  vessel  (large  in 
proportion  to  the  amount  of  oil  used)  with  its  own  volume,  or 
more,  of  water.  This  was  heated  until  the  water  boiled,  which 
of  course  helped  to  mix  the  oil  and  water,  so  that  the  latter  might 
dissolve  out  the  soluble  ingredients  of  the  former.  As  the  water 
evaporated  it  was  replaced  from  time  to  time,  and  after  boiling 
for  one  or  two  or  more  days  the  mixture  was  allowed  to  settle 
and  the  oil  poured  off.  This  method  was  further  complicated  by 
the  addition  of  salts  of  various  kinds  to  the  water. 

Separation  from  Water. — When  oil  is  treated  in  this  way  part 
of  it  is  likely  to  remain  as  a  persistent  emulsion  with  the  water. 
The  common  way  of  separating  these  emulsions  is  now  to  add 
common  salt,  which  makes  a  brine  of  the  water,  and  this  brine 
separates  easily  from  the  oil;  and  cloudy  oil  is  easily  cleared  by 
filtering  it  through  or  shaking  it  with  some  soluble  saline  sub- 
stance, previously  made  anhydrous  by  heating  it,  which  takes  out 
the  traces  of  water  which  produce  the  cloudiness.  White  vitrio 
(sulphate  of  zinc)  is  well  suited  for  this  purpose,  and  all  the  older 
recipes  which  recommend  this  salt  say  that  it  should  first  be  cal- 
cined. Green  vitriol  (sulphate  of  iron)  has  also  been  used,  but 
not  so  much. 

Driers. — When  zinc  sulphate  or  any  such  calcined  salt  is 
used  in  this  way  to  remove  water,  it  is  literally  a  drier.  It  makes 
the  oil  dry,  in  the  sense  that  it  frees  it  from  water,  and  I  cannot 
doubt  that  it  was  in  this  way  that  zinc  sulphate  came  to  be  spoken 
of  as  a  drier.  Of  course,  oil  which  has  in  this  or  any  other  way 
been  freed  from  water  will  oxidize,  and  in  that  sense  also  dry, 
faster  than  that  which  contains  water,  and  so  white  vitriol  and 
other  hygroscopic  salts  came  to  be  spoken  of  as  driers  and  con- 
fused with  that  other  class  of  driers,  of  which  litharge  is  a  type, 
which  do  not  absorb  water,  but  cause  oil  to  dry  or  harden  by 
increasing  its  chemical  activity,  a  function  which  the  zinc  salts 
(and  other  similar  substances)  do  not  appear  to  possess  in  the 
least  degree.  Even  with  the  most  improved  methods  a  great 
deal  of  the  freshly  pressed  oil  is  turbid  with  water  and  wet  matter, 
and  is  purified  by  long  settling  in  tanks,  followed  by  filtration. 


34  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

It  is  easy  to  understand  that  in  the  laboratory  of  the  painter, 
where  only  a  pint  or  two  of  oil  was  made  at  a  time,  it  was  easier 
to  clear  it  rapidly  by  treating  it  with  a  chemically  inactive  but 
hygroscopic  salt.  From  this  it  was  but  an  easy  step  to  regard 
the  saline  substance  as  having  a  beneficial  action  on  the  oil  itself. 
The  use  of  these  things,  such  as  the  sulphates  of  iron,  zinc,  and 
magnesia,  and  some  other  similar  substances,  has  not  yet  become 
entirely  obsolete,  although  in  the  way  they  are  used  they  are 
probably  absolutely  useless. 

"  Breaking  "  of  Oil. — It  has  long  been  known  that  if  freshly 
made  linseed-oil  is  heated,  without  the  addition  of  any  other 
substance,  to  about  400°  F.,  it  is  decomposed ;  a  considerable 
part  of  the  oil  appears  to  be  converted  into  a  gelatinous  substance. 
This  has  been  investigated  by  G.  W.  Thompson  (Journal  of  the 
American  Chemical  Society,  1903),  who  arrives  at  the  following 
conclusions : 

Although  the  amount  of  gelatinous  matter  appears  large, 
really  but  a  small  proportion,  less  than  a  third  of  one  per  cent,  of 
the  original  oil  is  actually  changed;  but  this  is  in  bulky  masses 
or  lumps,  swollen  by  the  absorption  of  a  large  amount  of  the 
unchanged  oil,  which  may  be  washed  out  of  it  by  the  use  of 
solvents.  When  this  is  done  and  the  decomposed  oil  is  analyzed 
it  is  found  to  contain  nearly  half  its  weight  of  mineral  matter, 
consisting  of  pyrophosphates  of  lime  and  magnesia,  and  amount- 
ing to  practically  all  the  mineral  matter  present  in  the  original 
oil.  As  it  has  been  often  claimed  that  mucilage  is  contained 
in  raw  oil  and  is  the  cause  of  its  "breaking,"  this  was  carefully 
looked  for  in  the  separated  portion,  but  none  was  found;  neither 
was  there  any  nitrogenous  matter.  It  seems  certain  that  albu- 
minous and  mucilaginous  matters  are  not  contained  in  clear, 
well-settled  oil. 

The  fact  that  the  "break"  of  linseed-oil  is  due  to  the  phos- 
phates it  contains  explains  the  well-known  method  of  refining 
oil  for  varnish-makers  by  treatment  with  a  little  acid,  which 
decomposes  and  removes  these  inorganic  constituents.  Treat- 
ment with  alkali  will  also  do  it ;  and  oil  which  has  been  moderately 


LINSEED-OIL.  35 

heated  and  has  had  air  blown  through  it  will  not  break.  This 
latter  method  has  been  used  by  the  English  varnish-makers  for 
many  years. 

Linseed-oil  is  a  yellow  or  sometimes  greenish-yellow  liquid. 
It  is  not  known  whether  it  is  colored  by  some  foreign  matter 
contained  in  the  seed  or  whether  the  pure  oily  matter  has  color 
of  its  own.  Nearly  all  books  which  treat  of  it  give  recipes  for 
bleaching  it  so  that  it  shall  be  colorless,  but  it  may  be  confidently 
asserted  that  no  one  ever  saw  any  water-white  linseed-oil,  not 
so  much  as  an  ounce. 

Bleached  Oil. — "Colorless"  linseed-oil  is  simply  that  which 
has  been  bleached  to  a  pale-yellow  color  by  some  of  the  means 
known  to  oil-refiners ;  usually  about  half  the  color  seems  to  be 
removed.  All  colored  vegetable  oils  are  bleached  when  exposed, 
especially  in  a  thin  film,  to  the  sun.  When  linseed-oil  which 
has  been  bleached  in  this  way  is  put  in  the  shade  its  color  comes 
back,  at  least  to  a  considerable  degree.  When  it  is  heated  to  a 
high  temperature,  especially  if  at  the  same  time  agitated  with 
air,  so  as  to  promote  its  oxidation,  it  is  decomposed  into  a  sticky, 
gelatinous  solid,  somewhat  translucent,  dark  yellow  or  brownish 
yellow  in  color.  This  is  soluble  in  caustic  soda,  making  a  soap, 
but  a  soap  very  different  in  its  qualities  from  ordinary  linseed- 
oil  soap,  showing  that  the  composition  of  the  oil  has  undergone 
a  radical  change.  When  oil  is  exposed  to  the  air  at  the  ordinary 
or  at  a  moderate  heat,  and  especially  if  in  a  thin  film,  or  if  air 
is  blown  through  it,  it  is  changed  into  a  tough  substance,  quite 
elastic,  somewhat  like  leather,  though  not  nearly  so  tough. 

Linoxyn. — This  oxidized  oil,  or  linoxyn,  is  a  very  insoluble 
substance.  It  resists  ordinary  solvents  and  weak  acids,  but 
is  easily  attacked  by  strong  acids  and  by  alkalies  in  all  degrees 
of  strength.  When  about  half  oxidized  it  is  soluble  in  the  usual 
solvents  for  oil — spirits  of  turpentine,  benzine,  ether,  etc. 

As  to  historical  records,  while,  for  reasons  already  given,  the 
writer  has  no  doubt  of  the  use  of  linseed-oil  from  early  times,  we 
have  no  unmistakable  mention  of  linseed-oil  earlier  than  the 
fifth  century,  when  it  is  incidentally  mentioned  by  Aetius,  a 


36  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

Greek  medical  writer.  It  is  interesting  to  note  that  Aetius  gives 
directions  for  making  walnut-oil,  saying  that  it  "is  prepared 
like  that  of  almonds,  either  by  pounding  or  pressing  the  nuts, 
•or  by  throwing  them,  after  they  had  been  bruised,  into  boiling 
water.  The  medicinal  uses  are  the  same,  but  it  has  a  use  besides 
these,  being  employed  by  gilders  or  encaustic  painters,  for  it  dries 
and  preserves  gildings  or  encaustic  paintings  for  a  long  time." 

Walnut-oil  was  not  by  any  means  new  in  his  time,  however, 
for  it,  as  well  as  poppy-oil,  is  described  by  Dioscorides  five 
hundred  years  earlier.  The  fact  that  these  common  things  are 
not  mentioned  in  such  historical  or  literary  writings  as  have 
•come  down  to  us  is,  therefore,  not  to  be  taken  as  an  indication 
that  they  were  unknown.  Dioscorides  describes  a  method  of 
bleaching  oils  which  will  bear  comparison  with  anything  we 
do  now. 

Dioscorides  on  Bleaching  Oil.  —  "Oil  is  bleached  in  this 
manner:  Select  it  of  a  light  color,  and  not  more  than  a  year 
old;  pour  about  five  gallons  into  a  new  earthenware  vessel  of 
an  open  form,  place  it  in  the  sun,  and  daily  at  noon  dip  and 
pour  back  the  oil  with  a  ladle,  beating  up  its  surface  till  by  con- 
stant agitation  it  is  thoroughly  mixed  and  made  to  foam.  It  is 
thus  to  be  treated  for  several  days.  If  it  be  not  sufficiently 
Heached  place  it  again  in  the  sun,  repeating  the  above  operation 
until  it  becomes  colorless." 

In  the  "Secreti"  of  Alessio,  prior  of  the  Gesuati  of  Florence, 
the  author  of  which  was  born  in  1475,  but  which  contains  recipes 
of  earlier  date  than  1350,  are  directions  for  refining  oil  by  washing 
it  with  water. 

The  use  of  driers,  especially  of  litharge,  is  probably  of  great 
antiquity.  Galen,  in  the  second  century,  who  speaks  of  the 
drying  character  of  linseed  and  hempseed,  also  says  that  litharge 
and  white  lead  are  drying  in  their  nature.  Marcellus,  in  the 
fourth  century,  gives  directions  to  "put  some  oil  in  a  new  vessel 
and  put  it  over  a  moderate  fire;  then  add  well-ground  litharge, 
sprinkling  it  little  by  little  with  the  hand.  Stir  it  constantly  till 
the  oil  begins  to  thicken." 


LINSEED-OIL.  37 

Eraclius,  who  was  certainly  earlier  than  Theophilus,  since 
much  of  his  MS.  was  included  by  the  latter  in  his  writings, 
speaks  of  white  lead  as  a  drier  for  linseed-oil  and  gives  the  follow- 
ing directions:  "Put  a  moderate  quantity  of  lime  into  oil  and 
heat  it,  continually  skimming  it;  add  white  lead  to  it,  according 
to  the  quantity  of  oil,  and  put  it  in  the  sun  for  a  month  or  more, 
stirring  it  frequently.  And  know  that  the  longer  it  remains  in 
the  sun  the  better  it  will  be.  Then  strain  it  and  distemper 
the  colors  with  it." 

Earliest  Use  of  Umber.  —  In  the  De  Mayerne  MS.  (which 
will  be  spoken  of  later)  there  is  a  letter  from  Joseph  Petitot  of 
Geneva,  brother  of  the  celebrated  enameller,  dated  1644,  in  which 
it  is  said  that  the  ordinary  drier  for  drying  oils  was  umber.  As 
the  drying  of  umber  is  due  to  manganese,  this  is  probably  the 
earliest  mention  of  manganese  as  a  drier.  The  De  Mayerne  MS. 
also  speaks  of  burning  off  oil  to  make  it  siccative,  a  practice 
still  followed,  especially  in  making  printers'  ink.  It  may  be 
that  this  latter  practice  was  known  to  the  early  varnish-makers, 
for  they  constantly  speak  of  boiling  oil  until  it  is  reduced  in 
volume  a  third  or  a  half,  which  might  perhaps  be  done  by  burn- 
ing off;  while  it  is,  if  not  impracticable,  certainly  never  attempted 
in  any  other  way  at  present.  There  is  good  reason  for  thinking 
that  lead  and  manganese  oxides,  used  as  driers,  act  by  absorbing 
oxygen  from  the  air,  thus  making  peroxidized  compounds,  then 
giving  up  a  portion  of  this  oxygen  to  the  oil,  then  re-absorbing 
more  oxygen,  and  so  on.  Thus  a  small  amount  of  lead  and 
manganese  may  serve  to  oxidize  a  large  amount  of  oil. 

Manganese  Advised  by  Faraday. — It  is  said  on  what  appears 
to  be  good  authority  that  the  use  of  manganese  compounds  for 
this  purpose  was  first  recommended,  and  on  purely  theoretical 
grounds,  by  Professor  Michael  Faraday,  because  manganese, 
like  lead,  exists  in  two  states  of  oxidation,  and  readily  passes 
from  either  of  these  to  the  other. 

Cobalt  and  Nickel  Driers;  Vanadium. — There  are  but  two 
other  metals  which  possess  this  property,  viz.,  cobalt  and  nickel, 
and  the  writer  of  this  has  found  it  possible  to  make  most  excellent 


38  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

driers  with  both  these  metals;  which  did  not,  however,  seem 
to  possess  any  advantages  over  those  made  with  lead  and  man- 
ganese, and  as  they  were  more  costly  they  were  not  made  on  a 
commercial  scale.  It  is  desired,  however,  to  call  especial  atten- 
tion to  the  fact  that  cobalt  and  nickel  driers  have  been  made, 
and  are  efficient,  because  it  is  commonly  said  in  books  on  the 
subject  that  lead  and  manganese  are  the  only  metals  which  can 
be  used  in  this  way.  The  writer  also  made  a  vanadium  com- 
pound which  was  a  highly  efficient  drier,  but  of  course  its  cost 
prevented  its  use.  The  mistaken  statement  above  referred  to 
is  to  be  found  even  in  so  excellent  a  work  as  that  on  Drying  Oils 
by  L.  E.  Andes  (of  Vienna),  which  can  be  highly  recommended 
to  those  seeking  detailed  information  in  regard  to  this  class  of 
oils,  including  many  not  well  known. 

Acetate  of  lead  and  borate  of  manganese  are  often  used,  but 
they  are  not  efficient  until  they  are  decomposed  by  heat  and 
the  acid  driven  off,  so  that  it  appears  that  the  same  results  could 
be  obtained  by  using  oxides  or  linoleates.  These  salts  (the 
acetate  and  borate)  are  white  in  color  and  for  that  reason  appeal 
to  the  prejudice  of  the  oil-  or  varnish-maker,  but  their  value  is 
greatly  overestimated.  Umber  is  often  used  as  a  drier  and, 
as  has  been  pointed  out,  its  use  is  of  some  antiquity;  it  contains 
manganese,  to  which  its  activity  is  doubtless  due. 

Linseed-oil  is  frequently  adulterated;  with  a  view  to  the  pre- 
vention of  this,  the  State  of  New  York  recently  employed  Dr. 
Mcllhiney  to  investigate  the  subject,  and  by  his  courtesy  I  am 
able  to  insert  here  a  copy  of  his  report.  This  is  the  most  recent 
and  in  my  opinion  the  most  valuable  paper  on  linseed-oil,  and  I 
feel  that  I  cannot  do  better  than  to  print  it,  especially  as  it  has 
not  been  heretofore  very  accessible  to  the  general  public. 


CHAPTER  V. 

LINSEED-OIL. 
By  Dr.  PARKER  C.  MC!LHINEY. 

LINSEED-OIL  is  the  oil  obtained  from  the  seeds  of  the  flax- 
plant,  Linum  usitatissimum.  Formerly  the  oil  used  in  the  United 
States  was  obtained  principally  from  Indian  and  other  foreign 
seed,  but  of  late  years  the  domestic  seed  has  gradually  replaced 
the  foreign,  although  considerable  quantities  of  Calcutta  seed 
are  still  imported.  The  oil  obtained  from  Calcutta  seed  usually 
commands  a  higher  price,  as  it  is  of  a  light  color,  and  is  by  some 
considered  superior  to  that  obtained  from  American  seed.  Any 
real  superiority  of  Calcutta  oil  is,  however,  difficult  to  define, 
and  it  is  likely  that  prejudice  in  favor  of  the  imported  article 
has  much  to  do  with  the  preference.  Calcutta  oil  is  generally 
sold  raw  and  is  largely  consumed  by  varnish-makers. 

Linseed  is  a  crop  which  has  a  very  exhausting  effect  upon 
the  soil,  and  it  is  for  this  reason  grown  in  the  United  States  mostly 
on  the  frontier  of  the  agricultural  territory.  The  result  of  this 
is  that  the  principal  sources  of  supply  for  domestic  seed  are 
gradually  moving  farther  west  and  northwest.  It  is  estimated 
that  13,000,000  to  14,000,000  bushels  of  flaxseed  were  grown 
in  the  United  States  in  1898,  and  that  the  production  in  1899 
will  reach  15,000,000  bushels.  The  usual  yield  of  oil  is  in  the 
neighborhood  of  2.3  gallons  per  bushel  of  seed. 

The  methods  of  extracting  the  oil  are  two,  by  extraction 
with  volatile  solvents  and  by  pressing.  The  extraction  method 
is  not,  to  my  knowledge,  practised  in  New  York  State.  To 
extract  the  oil  by  pressing,  the  seed  when  it  arrives  at  the  mill 
is  first  cleaned,  then  ground  to  meal  in  high-speed  rolls,  and 

39 


40  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

heated  by  steam.  In  some  mills  the  heating  is  done  by  steam 
injected  directly  into  the  meal  as  it  runs  in  a  stream  into  a  tub 
used  as  a  reservoir  of  hot  meal.  In  other  works  the  heating-tub 
is  steam- jacketed  and  no  free  steam  is  admitted  to  the  meal. 
From  the  heating-pan  the  meal  is  delivered  to  a  machine  which 
fills  it  into  canvas  forms  and  presses  these  forms  lightly  to  make 
them  keep  their  shape  sufficiently  to  handle.  They  are  then 
placed  in  hydraulic  presses  and  subjected  to  high  pressure,  caus- 
ing the  oil  to  run  out.  The  oil  at  this  stage  contains  various 
foreign  matters,  called  collectively  " foots,"  which  have  been 
pressed  out  with  the  oil.  These  are  removed  by  settling,  or  by 
filtration  through  cloth  and  paper  in  filter-presses,  or  by  both. 
The  separation  of  "foots"  on  storage  goes  on  for  a  long  time, 
and  the  oil  improves  by  storage  and  settling,  even  after  careful 
filtration. 

The  operation  of  "boiling  oil"  is  one  about  which  great 
secrecy  is  observed  by  the  manufacturers.  When  linseed-oil  is 
heated  to  a  temperature  of  300°  to  500°  F.,  its  drying  properties 
are  increased.  If  salts  of  lead  or  of  manganese  are  incorporated 
into  the  oil  a  similar  result  is  produced,  and  the  simplest,  and 
in  former  times  the  universal  method  of  increasing  the  drying 
properties  of  linseed-oil,  was  to  heat  the  oil  to  near  the  tempera- 
ture at  which  it  undergoes  destructive  distillation,  550°  F.,  or 
thereabouts,  and  stir  in  at  the  same  time  oxide  of  lead,  or  oxide 
of  manganese,  or  both.  Heating  the  oil  to  such  a  high  tempera- 
ture darkens  it  very  much,  and  as  light-colored  oil  is  often 
demanded,  so  that  the  oil  will  not  discolor  pigments  suspended 
in  it  more  than  necessary,  and  as  this  high  heat  is  wasteful  of 
oil,  time,  and  fuel,  it  has  become  the  practice  to  make  a  "drier" 
of  the  metallic  oxides  by  heating  them  with  a  small  portion  of 
the  oil  until  they  are  dissolved,  and  then  adding  this  drier  to 
the  main  body  of  the  oil  maintained  at  a  much  lower  tempera- 
ture, usually  not  much  above  the  boiling-point  of  water.  The 
result  of  this  process  is  that  there  is  not  so  great  a  loss  of  oil  dur- 
ing the  boiling,  and  the  oil  obtained  is  lighter  in  color.  The 
use  of  this  method  of  making  boiled  by  adding  to  raw  oil,  at  a 


LINSEED-OIL.  4r 

comparatively  low  temperature,  a  drier  made  by  a  separate 
operation,  has  induced  the  majority  of  makers  of  boiled  oil  ta 
buy  their  driers  from  a  varnish- manufacturer,  who  is  better 
equipped,  from  the  nature  of  his  business,  to  make  driers  than 
the  linseed-crusher  is.  The  division  of  labor  between  the  varnish- 
maker  and  the  linseed-oil  manufacturer  results  in  enabling  the 
linseed-crusher  to  dispense  with  all  apparatus  for  heating  oil 
to  very  high  temperaturers,  and  is  on  this  account  advantageous, 
to  him.  This  same  division  of  labor  has,  however,  had  the 
further  effect  of  allowing  the  manufacturer  of  driers  an  oppor- 
tunity to  introduce  into  them,  for  his  own  profit,  materials  which, 
the  oil-manufacturer  who  is  endeavoring  to  produce  a  pure 
article  would  not  wish  to  add  to  his  oil. 

It  is  claimed  by  the  makers  of  the  so-called  "bunghole"  oil 
(a  simple  mixture  of  raw  linseed-oil  with  drier),  and  also  by  the 
manufacturers  of  driers  to  be  used  in  this  way,  that  the  oil  made 
by  this  process  is  just  as  good  as  kettle-boiled  oil,  that  no  fraud  is 
intended  by  the  manufacturers  of  such  oil,  and  that,  in  fact, 
it  is  simply  a  variety  of  boiled  oil. 

On  the  other  hand  it  is  claimed  by  the  linseed-crushers  and 
others  who  make  boiled  oil  from  linseed-oil  and  metallic  oxides 
alone,  that  the  only  materials  which  it  is  necessary  to  add  to  a 
linseed-oil  in  converting  it  into  boiled  oil  are  the  oxides  of  lead 
and  manganese;  that  no  one  who  can  obtain  the  proper  facilities 
for  making  boiled  oil,  viz.,  a  kettle  in  which  it  can  be  .heated 
and  agitated,  finds  it  necessary  to  use  a  drier  thinned  with  benzine 
or  turpentine,  and  that,  in  fact,  these  are  in  the  finished  oil  simply 
dilutents  detracting  from  the  value  of  the  oil ;  that  it  is  not  neces- 
sary to  use  in  the  manufacture  of  drier  for  making  boiled  oil- 
any  shellac,  kauri-dust,  rosin,  or  rosin-oil,  or,  in  fact,  anything- 
but  linseed-oil,  lead,  and  manganese;  and  finally  that  the  sale 
as  "boiled  oil"  of  oil  which  contains  anything  but  linseed-oil, 
lead,  and  manganese  is  a  fraud  and  should  not  be  permitted. 

The  character  of  boiled  linseed-oil,  as  it  is  described  in  the 
literature,  even  in  the  latest  books,  does  not  agree  with  that  of 
the  oil  now  made  in  this  State.  It  is  described  in  the  literature 


42  TECHNOLOGY   OF  PAINT  AND   VARNISH 

as  being  made  at  a  high  temperature  in  the  old-fashioned  way, 
whereas  little,  if  any  oil  is  now  made  in  that  way.  There 
is  a  strong  prejudice  in  the  minds  of  most  of  the  users  of  boiled 
oil  in  favor  of  the  old-fashioned  "kettle-boiled"  oil.  Conse- 
quently the  manufacturers  are  somewhat  averse  to  admitting 
that  their  oils  are  made  after  the  modern  fashion,  although  no 
advantages  can  be  claimed  for  the  old  way.  This  prejudice  in 
favor  of  strongly  heated  oil  is  so  strong  that  the  dark  color  of 
the  old  oil  is  imitated  by  many  manufacturers  by  using  dark- 
colored  driers,  although  it  is  perfectly  evident  that  for  use  with 
all  light-colored  pigments  the  lighter  an  oil  is  in  color,  other 
things  being  equal,  the  more  desirable  the  oil  is.  This  prejudice 
seems  to  be  stronger  in  the  East  than  in  the  Western  States. 

Section  i  of  chapter  412  of  the  law  relating  to  linseed-  or 
flaxseed-oil  prohibits  the  manufacture  or  sale  as  boiled  linseed- 
oil  of  oil  which  has  not  been  heated  to  225°  F.  The  intention 
of  this  provision  is  undoubtedly  to  prevent  the  manufacture  of 
"  bunghole  "  oil,  but  it  is  difficult  to  understand  why  an  oil  should 
be  excluded  if  it  is  made  from  proper  materials  at  a  lower  tem- 
perature, and  still  more  difficult  for  an  analyst  to  ascertain  the 
temperature  to  which  the  oil  has  really  been  heated.  No  means 
are  known  to  me  by  which  it  is  possible  to  find  out  whether  a 
sample  of  boiled  linseed-oil  has  or  has  not  been  heated  to  225°  F. 

The  analytical  investigation  of  linseed-oil  and  its  adulterants 
was  carried  on  with  the  idea,  first,  of  ascertaining  the  character 
of  pure  linseed-oil  sold  in  New  York  State  by  various  manu- 
facturers; secondly,  to  ascertain  what  the  adulterants  commonly 
used  in  the  State  are;  and,  thirdly,  how  prevalent  the  practice 
of  adulteration  is.  With  these  ends  in  view,  a  series  of  samples 
was  obtained,  in  most  cases  directly  from  the  manufacturers, 
but  partly  also  from  large  users  of  the  oil,  which  are  of  undoubted 
commercial  purity.  Another  series  of  samples  was  obtained 
by  purchase  from  smaller  dealers.  Samples  of  oils  likely  to 
be  used  as  adulterants  were  obtained  from  manufacturers  or 
large  dealers. 


LINSEED-OIL.  43 


TESTS   FOR  PURITY  OF  OIL. 

The  tests  which  are  valuable  particularly  in  determining 
the  freedom  from  adulteration  are: 

1.  Specific  gravity. 

2.  The  action  of  bromine  or  iodine  on  the  oil.     Hubl  and 
bromine  figures. 

3.  The  percentage  of  unsaponifiable  organic  matter. 

4.  The  amount  of  alkali  required  to  convert  the  oil  into  soap. 
Kcettstorfer  figure. 

5.  The  amount  of  alkali  required  to  neutralize  the  free  acids  in 
the  oil.     Acid  figure. 

6.  The  percentage  of  insoluble  bromine  derivatives. 

7.  The  amount  of  volatile  oil  (turpentine  and  benzine)  con- 
tained in  the  oil. 

Other  tests  often  applied  to  linseed-oil  are  the  Maumene* 
test,  which  is  the  measurement  of  the  temperature  caused  by 
mixing  measured  amounts  of  the  oil  and  of  sulphuric  acid;  the 
amount  of  oxygen  absorbed  by  the  oil  when  exposed  to  the  air 
in  thin  films,  called  Livache's  test;  the  index  of  refraction;  and 
the  action  on  polarized  light. 

i.  The  Specific  Gravity. — Linseed-oil  is  heavier  than  most 
other  oils.  Its  specific  gravity  is  expressed  in  terms  of  water 
at  4°  C.  or  15°. 5  C.,  or  water  may  be  taken  as  unity  at  whatever 
temperature  the  determination  of  specific  gravity  is  made.  It 
is  advisable  that  some  standard  of  temperatures  should  be  set 
and  adhered  to  in  future  determinations,  as  exactness  and  sim- 
plicity are  above  all  else  necessary  in  work  that  may  be  submitted 
as  evidence  in  a  court  of  law.  It  is  at  all  events  advisable  that 
even  if  the  actual  determination  is  made  at  a  temperature  different 
from  the  standard,  it  should  be  expressed  in  terms  of  water  at 
the  standard  temperature.  Unfortunately  many  of  the  recorded 
determinations  do  not  state  either  the  temperature  at  which 
the  determination  was  made,  or  the  temperature  at  which  water 
is  taken  as  unity.  These  determinations  have  consequently 


44  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

little  legal  value.  I  should  recommend,  as  the  conditions  which 
combine  the  greatest  ease  with  the  best  accord  with  published 
data,  that  the  gravity  should  be  determined  at  i5°5.  C.,  water 
at  the  same  temperature  being  taken  as  unity.  Almost  all  the 
determinations  of  specific  gravity  given  in  this  report  were  made 
under  these  conditions. 

The  specific  gravity  of  linseed-oil  may  be  taken  with  the 
greatest  accuracy  by  means  of  a  specific-gravity  bottle,  the  weight 
of  which  is  determined  empty,  full  of  water  at  15°. 5  C.,  and 
filled  with  the  oil  to  be  examined  at  the  same  temperature. 
Another  very  convenient  laboratory  method  having  only  slightly 
inferior  accuracy,  and  the  method  by  which  almost  all  the  deter- 
minations given  in  this  report  were  obtained,  is  in  application 
of  the  principle  of  Mohr's  hydrostatic  balance,  by  using  a  plummet 
with  the  ordinary  analytical  balance.  For  rougher  work  a  deli- 
cate hydrometer  may  be  used. 

The  specific  gravity  of  raw  linseed-oil  is  given  by  Allen's 
Comm.  Org.  Anal.,  3d  ed.,  vol.  2,  part  i,  p.  147,  as  generally 
about  .935,  but  varying  from  .931  to  .937.  The  temperature 
is  not  stated,  but  it  is  presumably  15°.  5  C.  These  limits  are 
the  same  as  those  set  in  Benedikt,  Analyse  der  Fette  und  Wachs- 
arten,  3.  AufL,  p.  429,  and  no  oils  of  undoubted  purity  which  I 
have  examined  have  fallen  outside  of  these  limits.  It  may, 
therefore,  be  stated  as  an  established  fact  that  if  an  oil  has  a 
specific  gravity  at  i5°.5  C.,  water  at  the  same  temperature  being 
unity,  that  is  below  .931  or  above  .937,  it  is  not  pure  raw  linseed- 
oil. 

The  lower  limit  to  the  specific  gravity  of  boiled  linseed-oil 
may  be  set  at  the  same  point,  .931,  because  a  linseed-oil  can  only 
become  heavier  by  heating  with  access  of  air  and  the  addition  of 
metallic  oxides.  Oils  made  with  driers  containing  benzine  may 
have  lower  specific  gravities.  The  upper  limit  to  the  gravity  it 
is  difficult  and  indeed  impossible  to  set,  because  genuine  linseed- 
oil  may  be  raised  to  .950  or  higher  by  continued  heating,  though 
it  is  not  commonly  above  .940. 

Expansion  by  Heat. — The  change  in  gravity,  with  change  of 


LINSEED-OIL.  45 

temperature,  of  linseed-oil,  and  of  some  other  oils,  has  been  de- 
termined by  Allen,  Comm.  Org.  Anal.,  3d  ed.,  vol.  2,  part  i, 
p.  33,  and  the  following"  are  some  of  his  results: 

XT  A          e  r\-t  Correction  for 

Nature  of  Oil.  f0  c 

Linseed  ................................  000649 

Menhaden  .............................  000654 

Cottonseed  .............................  000629 

Rape  ..................................  000620 

According  to  the  results  obtained  by  Saussure,  the  coefficient 
of  expansion  of  linseed-oil  is  not  uniform  between  12°  C.  and  94°" 
C.  He  records  the  following  results  (Benedikt,  p.  428)  : 


Temperature. 

12°  C  .....................................  939 

25°  C  .....................................  930 

50°  C  .....................................  921 

94°  C  .....................................  881 

Calculating  from  these  results  we  obtain,  as  the  variation  for 
i°  C.,  between  12°  C.  and  25°  C.,  .000692;  between  25°  C.  and 
50°  C.,  .000360;  and  between  50°  C.  and  94°  C.,  .000909.  It 
will  be  seen  from  the  table  giving  the  results  of  determinations 
of  specific  gravity  at  different  temperatures  that  I  do  not  find  in 
the  oils  examined  a  similar  change  in  the  rate  of  expansion.  The 
averages  of  the  figures  obtained  with  raw  oils,  Nos.  52  and  73, 
and  boiled  oil,  No.  72>  show  that  the  change  in  specific  gravity 
for  i°  C.,  between  i5°.5  C.  and  28°  C.,  was  .000654;  between 
28°  C.  and  100°  C.,  .000720;  and  between  i5°.5  C.  and  100°  C., 
.000712. 

A  low  specific  gravity  in  an  oil  under  examination  might  be 
caused  by  the  presence  of  (i)  turpentine  or  benzine  (indicated 
also  by  odor);  (2)  heavier  petroleum-oils;  (3)  corn-  or  cottonseed- 
oils. 

A  high  specific  gravity  would  point  to  (i)  rosin  or  other  resin; 
(2)  rosin-oil;  (3)  excessive  heating  or  unusual  addition  of  me- 
tallic oxides. 


46  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

2.  The  Action  of  Bromine  or  Iodine  on  the  Oil. — Linseed-oil 
is  largely  composed  of  constituents  which  are  unsaturated,  and 
which  can,  therefore,  combine  by  direct  addition  with  2,  4,  or  6 
atoms  of  bromine  or  iodine.  Of  the  adulterants  of  linseed-oil, 
mineral  and  rosin  oils  and  rosin  itself  possess  this  power  only  to 
a  slight  degree,  and  none  of  the  other  adulterants  except  men- 
haden-oil possess  it  in  as  high  a  degree  as  linseed-oil.  Besides 
the  principal  action  of  bromine  or  iodine  upon  linseed-oil,  i.e., 
direct  addition  of  halogen,  another  action  takes  place  by  which 
one  half  of  the  halogen  which  disappears  enters  into  combination 
with  the  oil,  and  the  other  half  combines  with  hydrogen  which 
'the  first  half  has  replaced  in  the  oil. 

The  substitution  of  bromine  or  iodine  for  hydrogen  goes  on  to 
only  a  slight  extent  with  seed-oils  and  with  glycerides  in  general, 
but  with  .rosin,  rosin-oil,  and  mineral  oils,  the  case  is  very  differ- 
ent. It  has  been  proved  by  the  author  that  when  bromine  acts 
upon  rosin  and  upon  rosin-oil,  although  a  large  amount  of  bromine 
is  changed  from  the  free  into  the  combined  state,  almost  all  of  the 
bromine  is  taken  up  by  the  rosin  or  oil  by  substitution,  and  not 
by  addition,  and  in  the  case  of  ordinary  American  mineral  oils, 
that  taken  up  by  substitution  is  a  large  proportion  of  the  total 
absorption. 

The  process  in  most  common  use  for  determining  the  percent- 
age of  halogen  absorbed  by  oils  is  known  as  the  Hiibl  process; 
and  though,  by  its  use,  valuable  indications  as  to  the  purity  and 
value  of  linseed-oil  are  obtained,  it  unfortunately  does  not  dis- 
tinguish between  the  power  of  the  oil  to  absorb  halogen  by  addi- 
tion and  the  power  it  likewise  possesses  of  absorbing  halogen  by 
substitution.  The  Hiibl  process,  on  this  account,  fails  to  dis- 
criminate closely  between  rosin,  which  is  one  of  the  likeliest  con- 
stituents of  a  linseed-oil  substitute,  and  linseed-oil  itself,  as  the 
Hiibl  figures  for  the  two  substances  are  not  very  different. 

A  process  described  by  the  author  (J.  Amer.  Chem.  Soc.,  16, 
56),  similar  to  one  used  previously  by  Allen  for  testing  shale-oils, 
distinguishes  between  addition  and  substitution,  and  by  its  use 
the  presence  of  any  notable  amount  of  rosin,  rosin-oil,  or  mineral 


LIN  SEED -OIL.  47 

oil  can  be  detected  with  a  considerable  degree  of  accuracy,  and 
a  fair  idea  formed  of  the  character  of  the  adulterant. 

Hiibl  Process. — The  Hiibl  process  is  one  of  the  best-known 
methods  of  fat  analysis;  the  method  by  which  the  Hiibl  figures 
were  obtained  for  this  report  was  as  follows : 

A  solution  of  25  grams  of  iodine  and  30  grams  of  mercuric 
chloride  in  one  liter  of  alcohol  is  allowed  to  stand,  after  making, 
for  twenty-four  hours  in  the  dark  before  using.  Two  hundred 
milligrams  or  thereabout  of  the  oil  to  be  analyzed  is  weighed  into 
a  glass-stoppered  bottle,  10  cc.  of  chloroform  added  to  dissolve 
the  oil,  and  25  cc.  of  the  iodine  solution  added.  If  the  solution, 
when  shaken  to  mix  the  chloroform  and  alcoholic  liquid,  does  not 
become  clear,  5  cc.  more  of  chloroform  is  added.  The  bottle  is 
then  allowed  to  remain  in  the  dark  eighteen  hours,  and  at  the  end 
of  that  time  a  solution  of  potassium  iodide  is  added,  and  the  free 
iodine  in  the  solution  titrated  with  tenth-normal  sodium  thiosul- 
phate.  Twenty-five  cubic  centimeters  of  the  same  iodine  solution 
which  has  been  placed  in  a  similar  bottle  and  allowed  to  stand 
with  the  test  is  titrated  at  the  same  time  with  thiosulphate,  and 
the  difference  between  the  two  titrations  gives  the  amount  of 
iodine  absorbed  by  the  oil.  Full  discussions  of  the  process  are 
given  in  Benedikt,  Analyse  der  Fette  und  Wachsarten,  and  in 
Allen,  Commercial  Organic  Analysis,  Lewkowitsch,  Oils,  Fats, 
and  Waxes,  and  Gill,  Oil  Analysis. 

Mcllhiney's  Method  with  Bromine. — The  bromine  figures  were 
obtained  by  a  modification  of  the  author's  original  method.  The 
method  actually  used  was  as  follows: 

About  200  milligrams  of  the  oil  was  placed  in  a  dry  glass- 
stoppered  bottle,  10  cc.  of  carbon  tetrachloride  added  to  dissolve 
the  oil,  and  then  20  cc.  of  third-normal  bromine  in  carbon  tetra- 
chloride run  in  from  a  pipette.  Another  pipetteful  is  run  into 
another  similar  bottle.  It  is  convenient,  but  not  absolutely  neces- 
sary, that  both  bottles  should  now  be  cooled  by  immersing  them 
in  cracked  ice.  This  causes  the  formation  of  a  partial  vacuum  in 
the  bottle.  The  bromine  need  not  be  allowed  to  react  with  the 
oil  for  more  than  a  few  minutes,  as  the  reaction  between  them  is 


48  TECHNOLOGY  OF  PAINT  AND    VARNISH, 

nearly  instantaneous.  Twenty-five  cubic  centimeters  of  a  neutral 
10  per  cent,  solution  of  potassium  iodide  is  introduced  into  each 
bottle  by  slipping  a  piece  of  rubber  tubing  of  suitable  size  over 
the  lip  of  the  bottle,  pouring  the  iodine  solution  into  the  well  thus 
formed,  and  shifting  the  stopper  slightly  so  as  to  allow  the  solution 
to  be  sucked  into  the  bottle,  or,  if  the  bottle  has  not  been  cooled, 
to  cause  the  air  as  it  escapes  from  the  interior  to  be  washed  by 
bubbling  through  the  potassium  iodide  solution.  This  method  of 
introducing  the  iodide  solution  effectually  prevents  the  loss  of  any 
bromine  or  hydrobromic  acid.  As  soon  as  the  iodide  solution  has 
been  introduced,  the  bottle  is  shaken,  and  preferably  set  into  the 
ice  for  a  couple  of  minutes  more,  so  that  there  may  be  no  loss  of 
drops  of  the  solution  when  the  stopper  is  opened,  caused  by  a 
slight  pressure  inside  the  bottle.  The  reaction  between  the  bro- 
mine and  the  iodide  solution  causes  some  heat  and  consequent 
pressure.  The  free  iodine  is  now  titrated  with  neutral  tenth- 
normal  sodium  thiosulphate,  using  as  little  starch  as  possible  as 
indicator.  At  the  end  of  this  titration  5  cc.  of  a  neutral  2  per  cent, 
solution  of  potassium  iodate  and  a  little  more  starch  solution  are 
added  and  the  iodine  liberated,  on  account  of  the  hydrobromic 
acid  produced  in  the  original  reaction  of  bromine  on  the  oil, 
titrated  with  thiosulphate.  From  the  figures  so  obtained  the 
total  percentage  of  bromine  which  has  disappeared  is  calculated, 
and  the  percentage  of  bromine  found  as  hydrobromic  acid,  called 
the  "Bromine  Substitution  Figure,"  is  also  calculated,  while  from 
these  two  the  " Bromine  Addition  Figure"  is  obtained  by  sub- 
tracting twice  the  bromine  substitution  figure  from  the  total 
bromine  absorption.  A  consideration  of  the  figures  submitted  in 
the  table  will  show  that  if  an  oil  contains  rosin,  rosin-oil,  or  min- 
eral oil,  the  fact  will  be  brought  out  by  this  process,  and  an  indi- 
cation given  by  the  figures  so  obtained  as  to  which  one  is  present. 
If  the  bromine  substitution  figure  is  normal,  the  absence  of  more 
than  a  very  small  quantity  of  turpentine,  benzine,  rosin,  or  rosin- 
oil  is  assured.  The  process  can  be  carried  out  in  the  time  neces- 
sary for  weighing  and  titrations,  as  the  standard  solution,  unlike 
the  Hiibl  solution,  does  not  deteriorate  on  keeping,  if  tightly 


LINSEED-OIL.  49 

closed,  so  that  it  is  always  ready  for  immediate 'use,  and  there  is 
no  waiting  for  some  hours  for  the  reagents  to  act  upon  the  oil,  as 
in  the  Hiibl  process,  for  in  this  case  the  reaction  takes  place  im- 
mediately. 

It  will  be  seen  from  the  table  of  results  that  the  Bromine  Addi- 
tion Figure  of  linseed-oil  lies  ordinarily  between  100  and  no. 
The  low  figures  of  No.  i  and  No.  2  are  to  be  accounted  for  by 
the  fact  that  the  samples  are  several  years  old,  and  it  is  well 
known  that  keeping  lowers  the  halogen  figures  of  linseed-oil. 

A  low  Addition  Figure  may  also  be  caused  by  the  presence  of 
rosin,  rosin-oil,  benzine,  or  mineral  oils,  which  have  figures  usually 
below  15;  by  the  presence  of  some  other  seed-oil,  the  commonest 
of  this  class  being  corn-  and  cottonseed-oils,  having  figures  in 
the  neighborhood  of  73  and  63  respectively;  or  by  the  oil,  in 
case  it  is  a  boiled  oil,  having  been  boiled  in  the  old-fashioned 
way  at  a  high  temperature. 

If  the  Addition  Figure  is  very  much  higher  than  no,  it  will 
be  found  that  the  oil  contains  turpentine,  as  all  other  foreign 
materials  added  have  lower  figures  than  linseed-oil. 

The  Bromine  Substitution  Figure  of  genuine  linseed-oil  is 
commonly  about  3.  A  much  higher  figure  would  point  to  tur- 
pentine, rosin,  or  rosin-oil,  which  give  figures  from  20  to  90 ;  to 
the  presence  of  some  petroleum  product,  as  benzine,  having  a 
figure  in  the  neighborhood  of  15,  or  a  heavier  petroleum-oil, 
which  may  have  as  low  a  figure  as  linseed,  or  may  be  much  higher; 
or  to  the  presence  of  mineral  acid  in  the  oil,  which  may  be  allowed 
for  by  a  separate  determination  of  its  amount,  as  described  under 
the  determination  of  the  Acid  Figure. 

The  Hiibl  figure  of  raw  linseed-oil  is  given  by  Benedikt  from 
148.8  to  183.4.  Boiled  oil,  according  to  the  same  author,  may 
give  figures  below  100.  Allen  gives  the  figures  for  raw  oil  between 
170  and  181.  Rowland  Williams  states  that  a  very  large  number 
of  raw  linseed-oils  examined  by  him  almost  all  gave  figures 
above  180.  The  figure  is  reduced  by  keeping.  From  the  table 
of  results  obtained  upon  the  oils  examined  it  will  be  seen  that 
the  figure  of  pure  oil  is  commonly  in  the  neighborhood  of  178. 


50  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

It  is  a  noteworthy  fact  that  both  the  Hubl  and  the  Bromine 
Addition  Figures  are  practically  the  same  for  boiled  oil  as  now 
made  as  for  raw  oil,  whereas  boiled  oil  made  by  the  old  process  at 
a  high  temperature  gave  distinctly  lowTer  figures  on  account  of  the 
effects  of  the  high  heat  upon  the  oil. 

In  order  to  facilitate  comparison  between  the  Hubl  and  the 
bromine  figures  of  the  oils  examined,  the  amount  of  bromine 
equivalent  to  the  iodine  absorbed  as  expressed  by  the  Hubl 
figure  has  been  calculated,  and  by  dividing  this  result  by  the 
Bromine  Addition  Figure  a  figure  was  obtained  for  each  oil 
which  is  intended  to  express,  by  the  amount  it  exceeds  i.ooo, 
the  amount  of  substitution  of  iodine  which  has  gone  on  in  the 
Hubl  iodine  absorption.  For  example,  if  the  figure  obtained 
for  an  oil  by  the  calculation  described  is  found  to  be  1.075,  ^ 
indicates  that  the  Hubl  figure  is  in  that  case  7.5  per  cent,  higher 
than  the  true  iodine  figure  which  should  express  the  iodine  absorp- 
tion by  addition. 

The  Hubl  figures  of  a  number  of  the  oils  received  last  were 
not  determined,  because  it  did  not  appear  that  the  determina- 
tions would  add  any  information  to  that  given  more  fully  by  the 
bromine  figures. 

It  is  not  believed  that  the  Bromine  Addition  Figure  is  sensibly 
affected  by  the  length  of  time  that  the  oil  is  allowed  to  remain 
in  contact  with  bromine,  but  the  Bromine  Substitution  Figure 
probably  is.  The  effect  of  the  difference  between  five  minutes' 
and  thirty  minutes'  contact  does  not  appear,  however,  to  be 
marked,  unless  the  substitution  figure  is  very  high,  as  in  the  case 
of  pure  resin  or  turpentine.  The  results,  reported  were  obtained 
by  about  fifteen  minutes  contact. 

In  carrying  out  either  the  Hubl  or  the  bromine  process  upon 
oils  it  is  necessary  that  an  excess  of  iodine  or  bromine  should  be 
used  amounting  to  as  much  as  the  oil  absorbs.  Many  iodine 
figures  on  record  are  too  low  because  this  precaution  was  not 
attended  to. 

It  is  believed  that  more  information  is  to  be  obtained  as  to  the 
character  of  a  sample  of  linseed-oil  by  determining  the  bromine 


LINSEED-OIL,  51 

figures  than  by  any  other  single  test.  In  the  case  of  an  oil  of 
unknown  character  it  would  in  most  cases  be  advisable  to  apply 
this  test  first  to  it. 

3.  The  Percentage  of  Unsaponifiable  Organic  Matter. — Lin- 
seed-oil, being  composed  almost  entirely  of  fatty  matter  of  the 
ordinary  type,  compounds  of  fatty  acids  with  glycerin,  gives 
only  a  small  percentage  of  material  which  cannot  be  saponified. 
The  amount  to  be  found  in  raw  linseed-oil  has  been  investigated 
by  Thompson  and  Ballantyne  (J.  Soc.  Chem.  Ind.,  1891,  10,  336), 
who  find  amounts  varying  from).  1.09  to  1.28  per  cent,  in  oil  from 
various  sources,  and  by  Rowland  Williams  (J.  Soc.  Chem.  Ind., 
1898,  17,  305),  who  finds  that  it  varies  from  0.8  to  1.3  per  cent. 
Williams,  loc.  cit.,  has  also  determined  the  amount  of  unsaponi- 
fiable  matter  in  boiled  oil,  and  finds  that  the  amount  is  nearly 
twice  as  great  as  in  raw  oil,  his  figures  for  boiled  oil  being  1.3  to 
2.3  percent.;  being  usually  about  2  per  cent.  Williams  regards 
any  oil  with  a  percentage  of  unsaponifiable  matter  higher  than  2.5 
as  adulterated.  His  statements  refer  to  oil  which  has  been  boiled 
at  a  high  temperature,  and  the  boiled  oils  for  sale  in  New  York 
State  are  apparently  all  made  at  too  low  a  temperature  to  cause 
any  increase  in  the  amount  of  unsaponifiable  matter  contained, 
with  the  exception  of  the  oil  in  the  drier.  In  view  of  these  facts, 
2.5  per  cent,  would  be  a  reasonable  limit  to  the  amount  of 
unsaponifiable  matter  in  linseed-oil.  This  is  so  well  established 
that  it  was  not  thought  advisable  to  make  this  determination 
upon  the  pure  oils  examined. 

It  may  be  noted  that  in  case  an  oil  is  found  to  contain 
unsaponifiable  matter  in  excessive  amount,  the  evidence  which 
can  be  furnished  the  prosecution  may  be  made  of  the  most  con- 
clusive character,  for  the  adulterant  can  be  actually  separated 
from  the  genuine  linseed-oil  and  exhibited,  whereas,  in  the  case 
of  some  other  adulterants,  the  evidence,  though  it  may  be  con- 
clusive, is  of  a  character  requiring  more  demonstration  to  one 
unfamiliar  with  the  scientific  examination  of  oils.  The  adul- 
terants whose  presence  can  in  this  way  be  demonstrated  by 
actual  separation  are  mineral  oil  and  usually  rosin-oil.  Benzine 


52  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

and  turpentine,  although  unsaponifiable,  are  not  found  with  the 
unsaponifiable  matter,  as,  from  the  nature  of  the  methods  of 
analysis,  only  materials  that  are  practically  non-volatile  are 
counted  as  unsaponifiable.  They  are  easily  separated  and 
determined,  however,  as  volatile  oil. 

There  are  several  methods  for  determining  the  percentage  of 
unsaponifiable  material,  proposed  by  different  experimenters. 
Some  treat  the  oil  with  alcoholic  or  aqueous  solution  of  potash 
or  soda,  evaporate  off  the  alcohol  or  water,  and  treat  the  dried 
soap  with  petroleum  ether  or  chloroform  to  dissolve  the  unsapon- 
ifiable portion.  Other  experimenters,  after  saponifying  the 
soap  with  alcoholic  solution  of  potash  and  evaporating  off  the 
alcohol,  dissolve  the  resulting  soap  in  water  and  agitate  the  solu- 
tion with  ether  several  times  to  remove  from  the  soap  solution 
the  unsapon  fiable  matter  which  it  holds  in  suspension. 

A  method  which  can  with  safety  be  recommended  for  deter- 
mining unsaponifiable  matter  in  linseed-oil  is  substantially  that 
described  in  Allen,  Comm.  Org.  Anal,  3d  ed.,  vol.  2,  part  i, 
p.  112.  A  quantity  of  oil  varying  from  i  to  10  grams,  depending 
upon  the  amount  of  unsaponifiable  matter  present,  is  boiled  for 
two  hours,  with  frequent  shaking,  with  excess  of  alcoholic  solu- 
tion of  caustic  potash,  in  a  flask  provided  with  a  return  condenser. 
The  alcohol  is  then  distilled  off  until  only  a  small  quantity  remains. 
The  soap  is  then  dissolved  in  water,  using  75  to  100  cc.  for  the 
purpose,  transferred  to  a  tapped  separator,  and  50  cc.  of  ether 
added.  The  liquids  are  then  mixed  by  shaking  and  allowed  to 
settle.  The  aqueous  liquid  is  then  drawn  off,  the  ethereal  layer 
washed  with  a  few  cubic  centimeters  of  water  to  which  a  little 
caustic  potash  has  been  added,  and  poured  into  a  tared  flask. 
The  soap  solution  is  then  returned  to  the  separator  and  extracted 
with  another  50  cc.  of  ether  in  the  same  way.  The  combined 
ethereal  solutions  are  evaporated  on  the  water-bath,  and  when 
the  ether  has  been  completely  removed  the  flask  now  containing 
the  unsaponifiable  matter  is  weighed.  If  the  percentage  of 
unsaponifiable  matter  found  is  large,  it  may  be  advisable  to 
repeat  the  process  of  saponification  and  extraction  upon  the 


LIN  SEED -OIL.  53 

unsaponifiable   matter,    in   order   to   be   quite   certain   that   no 
unsaponifiable  oil  has  escaped  the  action  of  the  alkali. 

Determination  of  Mineral  Oil. — The  mineral  oil  may  be 
separated  from  the  rosin-oil  in  the  unsaponifiable  material  found 
in  the  saponificatiqn  process  by  the  method  suggested  by  the 
author  in  the  Jour.  Amer.  Chem.  Soc.,  16,  385. 

Fifty  cubic  centimeters  of  nitric  acid  of  1.2  sp.  gr.  are  heated 
to  boiling  in  a  flask  of  700  cc.  capacity.  The  source  of  heat  is 
removed,  and  5  grams  of  the  oil  to  be  analyzed  added.  The 
flask  is  then  heated  on  the  water-bath,  with  frequent  shaking, 
for  fifteen  to  twenty  minutes,  and  about  400  cc.  of  cold  water 
added.  After  the  liquid  has  become  entirely  cold  50  cc.  of 
petroleum  ether  are  added  and  the  flask  is  agitated.  The  oil 
which  remains  unacted  upon  dissolves  in  the  ether,  while  the 
rosin  remains  in  suspension.  The  liquid  is  poured  into  a  tapped 
separator,  leaving  the  lumps  of  solid  rosin  as  far  as  possible 
behind  in  the  flask.  After  settling,  the  aqueous  liquid  is  drawn 
off  and  the  ethereal  layer  poured  into  a  tared  flask.  Another 
portion  of  petroleum  ether  is  added  to  the  rosin  remaining  in  the 
flask,  and  allowed  to  act  upon  it  for  about  ten  minutes,  when 
it  is  added  to  that  in  the  tared  flask.  After  distilling  off  the 
ether,  the  oil  is  weighed.  Mineral  oils  lose  about  10  per  cent, 
in  this  way,  and  hence  the  weight  of  oil  found  must  be  divided 
by  0.9  in  order  to  find  the  amount  present  in  the  sample  analyzed. 

Allen  found  mineral  oils  to  lose  10  to  12  per  cent,  on  treatment ' 
with  nitric  acid.     (Pharm.  Jour.,  3d  series,  n,  266.) 

Rosin-oil,  though  principally  composed  of  hydrocarbons,  may 
contain  some  unchanged  rosin  which  is  saponifiable,  and  conse- 
quently, in  case  rosin-oil  is  present,  the  amount  of  unsaponifiable 
matter  which  it  furnishes  is  less  than  the  total  amount  of  rosin- 
oil  present.  The  proportion  between  that  found  and  the  amount 
present  will  vary  according  to  the  way  in  which  the  oil  was  manu- 
factured, and  its  consequent  contents  in  unchanged  rosin.  Ordi- 
narily the  amount  of  saponifiable  matter  found  due  to  rosin-oil 
is  likely  to  be  about  nine-tenths  of  that  present. 

The   amount   of  unsaponifiable   matter  found   in  the   other 


54  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

animal  and  vegetable  oils  used  as  linseed-oil  adulterants  is 
approximately  the  same  as  that  found  in  linseed-oil  itself;  hence 
the  process  does  not  furnish  any  clue  to  corn-,  cottonseed-,  or 
menhaden-oils,  if  they  are  present. 

Petroleum-oils  may  be  used  in  adulterating  linseed-oil,  which 
are  just  on  the  border-line  between  volatile  and  practically  non- 
volatile oils.  Such  oil  as,  for  example,  kerosene  would  partly 
distil  off  with  the  alcohol  in  removing  it  after  saponification, 
while  the  rest  of  it  would  remain  to  be  extracted  with  ether  from 
the  aqueous  soap  solution,  and  be  weighed  as  unsaponifiable 
matter.  It  might  easily  happen  in  such  a  case  that  the  proportion 
of  the  partly  volatile  oil  which  would  be  obtained. by  distillation 
with  steam  in  the  determination  of  volatile  oil  would  be  a  dif- 
ferent one  from  the  proportion  removed  from  the  saponified 
oil  in  distilling  off  the  alcohol  in  the  determination  of  unsaponi- 
fiable matters,  and  that  the  sum  of  the  "volatile  oil"  and  of 
the  "unsaponifiable  matter"  would  be  more  or  less  than  the 
true  total  amount  of  adulterant  added.  In  such  a  case  it  would 
be  advisable  to  use  for  the  determination  of  unsaponifiable  matter 
a  portion  of  the  residue  from  the  determination  of  volatile  oil. 
V  4.  The  Amount  of  Alkali  Required  to  Convert  the  Oil  into 

Soap.  Koettstorfer  Figure. — This  determination  serves  in  the 
analysis  of  linseed-oil  as  an  indication  of  the  presence  or  absence 
of  unsaponifiable  matter,  whether  volatile  or  not.  Its  indications 
"  are  not  as  valuable  for  this  purpose  as  an  actual  determination 
of  the  unsaponifiable  matter  itself,  but  they  are  more  readily 
obtained.  The  determination  is  made  by  the  well-known 
Koettstorfer  process.  About  2.5  grams  of  the  oil  is  weighed 
into  a  flask,  25  cc.  of  half-normal  alcoholic  solution  of  caustic 
potash  added  and  the  liquid  boiled  on  the  water-bath  with 
a  return  condenser,  with  frequent  shaking,  for  about  two  hours. 
The  liquid  in  the  flask  is  then  titrated  with  half-normal  hydro- 
chloric acid,  using  phenolphthalein  as  indicator.  Twenty-five 
cubic  centimeters  of  the  same  alcoholic  caustic  potash  is  titrated 
at  the  same  time,  and  the  difference  between  the  two  titrations 
gives  the  alkali  used  in  saponifying  the  oil,  and  when  calculated 


LINSEED-OIL.       •  55 

in  milligrams  of  potassium  hydroxide  to  a  gram  of  oil  it  is  called 
the  "  Koettstorfer  Figure." 

The  Koettstorfer  Figure  of  raw  linseed-oil  is  given  by  Benedikt 
from  187.6  to  195.2,  and  by  Allen  from  187.4  to  195.2.  Bene- 
dikt's  figures  for  boiled  oil  are  from  180  to  190,  and  Allen's  figure, 
calculated  from  his  "  Saponification  Equivalent,"  is  188.  Bene- 
dikt's  figures  are  on  the  authority  of  Filsinger,  Chem.  Zeit.,  1894, 
1 8,  1867,  and  evidently  apply  to  old-fashioned,  strongly  heated 
boiled  oil.  Both  the  exposure  to  high  heat  and  the  introduction 
of  manganese  and  lead  soaps  of  linseed-oil  in  the  drier  tend  to 
reduce  the  Koettstorfer  figure.  Of  the  two,  exposure  to  high  heat 
for  a  long  time,  as  in  the  old-fashioned  boiling  process,  reduces  it 
far  more  than  the  introduction  of  the  small  percentage  of  lead 
and  manganese  soaps  as  used  in  practice.  The  boiled  oils  now 
for  sale  in  this  State  have,  as  will  be  seen  from  the  table,  almost 
as  high  figures  as  the  raw  oils.  It  may  fairly  be  demanded  of  a 
raw  oil  that  its  figure  shall  not  be  lower  than  187,  and  of  a  boiled 
oil  not  lower  than  186. 

A  low  figure  indicates  the  presence  of  mineral  oil,  having  a 
figure  below  10;  of  rosin-oil,  having  a  figure  below  20;  or  of  ben- 
zine or  turpentine,  of  both  of  which  the  figures  are  practically  o.o. 
Pure  hydrocarbons  give  a  Koettstorfer  figure  of  o.o,  but  mineral 
oils  usually  contain  traces  either  of  mineral  acid  from  the  refining 
process,  or  of  organic  acids  from  oxidation  by  the  air,  and  rosin- 
oils  contain  some  unchanged  rosin,  which  accounts  for  the  Kcetts- 
torfer  figures. 

5.  The  Amount  of  Alkali  Required  to  Neutralize  the  Free 
Acids  in  the  Oil.  Acid  Figure. — Perfectly  pure  linseed-oil  con- 
tains only  a  very  small  percentage  of  free  acids,  while  rosin  is  com- 
posed principally  of  free  acids,  and  rosin-oil  usually  contains  a 
notable  proportion  of  free  rosin.  Therefore,  the  free  acids  in  an 
oil  which  contains  rosin  will  neutralize  a  larger  proportion  of  alkali 
than  those  in  pure  linseed-oil.  On  keeping,  the  amount  of  free 
acid  is  likely  to  increase  somewhat.  The  free  acid  found  may  be 
partly  due  to  mineral  acid  used  in  refining  the  oil.  The  amount 
of  mineral  acid  may  be  separately  determined  by  boiling  for  some 


56  TECHNOLOGY   OF   PAINT  AND    VARNISH. 

• 

time  a  weighed  portion  of  the  oil  with  water,  cooling  the  mixture, 
adding  neutral  potassium  iodide  and  iodate,  and  titrating  the  lib- 
erated iodine  in  the  aqueous  solution  with  standard  sodium  thio- 
sulphate.  After  deducting  from  the  total  percentage  of  potash 
required  to  neutralize  the  total  free  acid  the  percentage  required  for 
the  mineral  acid,  the  percentage  required  by  the  free  organic  acid 
is  found,  which,  in  the  case  of  linseed-oil,  are  almost  certain  to 
be  either  the  normal  fatty  acids  from  the  linseed-oils  or  a  com- 
bination of  these  with  rosin  acids. 

The  method  of  determining  free  acids  is  to  weigh  5  to  10  grams 
of  the  oil  in  a  flask,  add  about  50  cc.  of  alcohol,  which  is  neutral 
to  phenolphthalein,  heat  on  the  water-bath  till  the  alcohol  boils, 
shake  well,  and  titrate  with  half -normal  alkali.  The  results  of 
the  titration  are  expressed  in  milligrams  of  potassium  hydroxide 
required  per  gram  of  oil,  and  the  result  is  called  the  "Acid 
Figure." 

Benedikt  gives  as  the  limits  observed  by  Nordlinger,  in  exam- 
ining ten  samples  of  linseed-oil,  acidities  from  .41  to  4.19  percent, 
of  oleic  acid,  corresponding  to  acid  figures  from  .9  to  8.3.  Mills 
allows  a  maximum  figure  of  10.0.  As  will  be  seen  from  the  figures 
contained  in  the  table,  raw  linseed-oil  will  usually  give  an  acid 
figure  in  the  neighborhood  of  3.0.  The  figure  of  oil  No.  i,  though 
pure,  is  7.1,  due,  no  doubt,  to  the  fact  that  it  is  several  years  old. 
The  figures  of  boiled  oil  are  slightly  higher,  due  probably  to  the 
production  of  a  small  quantity  of  some  acid  body  by  the  action 
of  heat  on  the  oil.  The  figure  of  boiled  oil  will  usually  be  below 
5,  but  is  more  uncertain  than  that  of  raw  oil.  A  figure  higher 
than  10.0  will  almost  certainly  be  found  due  to  the  presence  of 
rosin.  The  acid  figure  of  rosin  is  variously  given  by  Benedikt, 
Williams,  and  Schmidt  &  Erban,  from  145.5  to  179.2.  Samples 
examined  by  the  author  (Jour.  Amer.  Chem.  Soc.,  16,  275)  gave 
figures  from  155.7  to  168.5.  Fortunately  rosin  is  also  indicated 
by  a  high  Bromine  Substitution  Figure  and  a  low  Bromine  Addi- 
tion Figure,  and  if  all  three  point  to  rosin,  it  is  probably  there, 
but  the  safest  course  is  the  actual  isolation  of  the  rosin  by  Twit- 
chell's  or  Cladding's  process. 


LIN  SEED -OIL.  57 

6.  The  Percentage  of  Insoluble  Bromine  Derivatives. — This 
determination  is  proposed  by  Hehner  and  Mitchell  (Analyst,  Dec., 
1898,  vol.  23,  p.  310).     It  depends  upon  the  fact  that  linseed-oil 
gives,  when  dissolved  in  ether  and  treated  with  bromine,  com- 
pounds of    glycerides  and  bromine  which  are  insoluble  in  the 
ether,  while  oil  containing  glycerides  of  oleic  acid  only,  and  even 
semi-drying  oils  like  cottonseed-  and  corn-oils,  give  soluble  com- 
pounds.    Hehner  and  Mitchell  obtain  the  following  percentages 
of  insoluble  bromine  compounds  from  different  oils : 

Q.J  Per  Cent,  of  Insoluble 

Bromine  Compounds. 

Linseed-oil 23 . 86  to  25 . 8 

Poppy-oil o.o 

Corn-oil o.o 

Cottonseed-oil o.o 

Olive-oil o.o 

Almond-oil o.o 

Rapeseed-oil o.o 

Whale-oil 25.0 

Cod-oil 35 . 5 

Cod-liver  oil 42.9 

Shark-oil 22.0 

The  process,  which  seems  to  be  a  valuable  one  in  detecting 
adulterations  of  linseed-oil  with  other  seed-oils,  was  not  pub- 
lished until  late  in  the  progress  of  this  investigation,  and  it  was 
impossible  to  carry  on  all  the  experiments  with  it  that  it  deserves. 
It  has  seemed  inadvisable,  therefore,  to  present  in  full  the  results 
obtained.  Two  samples  of  raw  linseed-,  six  samples  of  boiled 
linseed-,  two  of  corn-,  and  one  of  cottonseed-oil  gave  results 
agreeing  substantially  with  those  of  Hehner  and  Mitchell.  Two 
samples  of  mineral  oil,  one  light  and  one  heavy,  one  sample  of 
rosin-oil,  and  one  sample  of  turpentine  failed  to  give  any  precipi- 
tate of  insoluble  bromine  derivatives. 

7.  The  Percentage  of  Volatile  Oil. — The  presence  of  even  a 
small  percentage  of  turpentine  in  linseed-oil  is  distinctly  indicated 
by  the  odor  of  the  oil  when  placed  in  a  vessel  which  it  about  half 


$8  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

fills,  the  vessel  closed,  and  heated  in  boiling  water  for  a  few  min- 
utes. The  smell  of  turpentine  will  then  be  noticed  en  opening 
the  vessel.  Benzine  is  indicated,  though  not  quite  so  distinctly, 
in  the  same  way. 

To  determine  the  amount  present,  a  convenient  quantity,  say 
300  grams,  is  heated  by  means  of  a  paraffin-  or  air-bath  to  about 
130°  C.,  in  a  flask  provided  with  an  outlet-tube  for  vapors,  an 
inlet-tube  reaching  nearly  to  the  bottom  of  the  vessel,  and  a  ther- 
mometer inserted  into  the  oil.  When  the  oil  has  reached  the 
desired  temperature  a  current  of  dry  steam  is  passed  through  the 
oil  and  the  vapors  condensed  in  a  Liebig  condenser.  The  distil- 
late will  separate  into  a  lower  layer  of  water  and  an  upper  layer 
of  volatile  oil,  which  is  separated  and  measured  or  weighed.  The 
aqueous  part  of  the  distillate  will  inevitably  carry  with  it  a  small 
quantity  of  volatile  oil,  but  the  quantity  is  very  small.  The 
amount  of  turpentine  either  dissolved  or  permanently  held  in 
suspension  by  water  was  found  in  one  experiment  made  by  the 
author  (Jour.  Amer.  Chem.  Soc.,  16,  273)  to  amount  to  0.300  gram 
in  90  cc.  of  water. 

A  separation  of  the  benzine  and  turpentine  in  the  volatile  oil 
found  is  best  effected  by  the  method  of  Burton  (Amer.  Chem.  J., 
12,  102),  which  depends  upon  the  difference  between  the  action  of 
fuming  nitric  acid  upon  benzine  and  upon  turpentine,  the  former 
remaining  practically  unattacked,  while  the  latter  is  strongly  acted 
upon  and  converted  into  bodies  soluble  in  hot  water.  The  method 
may  be  described  as  follows:  A  measured  quantity  of  the  mixture 
to  be  separated  is  allowed  to  drop  slowly  into  300  c.c  of  fuming 
nitric  acid  contained  in  a  flask  of  750  cc.  capacity,  provided  with 
a  return  condenser  and  immersed  in  cold  water.  A  violent  reac- 
tion takes  place  as  each  drop  of  oil  strikes  the  acid,  and  the  flask 
should  be  shaken  occasionally.  When  all  the  oil  has  been  added 
the  flask  is  allowed  to  stand  till  all  action  is  over.  The  contents 
of  the  flask  are  then  poured  into  a  separat ing-funnel  and  treated 
with  successive  portions  of  hot  water;  the  products  of  the  action 
of  the  acid  on  the  turpentine  are  in  this  way  removed,  leaving  the 
petroleum  oil  to  be  separated  and  measured. 


LINSEED-OIL.  59 

The  Maumene  Test. — When  oils  are  mixed  with  concentrated 
sulphuric  acid  the  mixture  becomes  hot,  and  the  rise  of  tem- 
perature varies  with  the  nature  of  the  oil.  The  chemistry  of  the 
process  is  but  slightly  understood.  Non-drying  oils  do  not  give 
as  great  a  rise  as  drying  oils,  and  consequently  linseed-oil  gives 
a  greater  rise  than  any  of  its  adulterants,  except,  unfortunately, 
menhaden-oil.  The  behavior  with  sulphuric  acid  is  similar  to  the 
behavior  with  bromine  and  iodine,  so  that  no  more  information 
is  gained  from  the  rise  in  temperature  than  is  obtained  by  deter- 
mining the  percentage  of  halogen  absorbed,  except  in  the  case  of 
adulteration  with  menhaden-oil. 

The  test  which  is  known  as  Maumene^s  test  and  which  is  fully 
described  in  Benedikt,  Analyse  der  Fette,  and  in  Allen,  Comm. 
Org.  Anal.,  vol.  2,  is  carried  out  by  mixing  50  cc.  of  the  oil  to 
be  examined  with  10  cc.  of  strong  sulphuric  acid.  The  reaction 
with  linseed-oil  and  with  some  other  oils  is  so  violent  that  the  oil 
must  be  diluted  with  some  more  inert  oil,  or  the  mixture  will  froth 
over.  The  rise  in  temperature  is  observed  by  a  thermometer  used 
to  stir  the  mixture,  and  the  vessel  in  which  the  experiment  is  car- 
ried on  is  protected  from  rapid  cooling  by  setting  it  inside  another 
larger  vessel,  usually  with  cotton  wool  between.  The  amount  of 
heat  abstracted  by  the  vessel  itself  depends  upon  its  mass  and 
material,  and  the  amount  of  loss  by  radiation  is  dependent  upon 
a  variety  of  circumstances.  Consequently  the  results  obtained  by 
different  observers  with  different  apparatus  have  varied  with  the 
same  oil,  and  each  apparatus  must  be  standardized  by  the  observer 
by  testing  with  a  number  of  oils  of  known  purity,  or  else  by  adopt- 
ing the  suggestion  of  Thomson  and  Ballantyne  (J.  Soc.  Chem.  Ind., 
1891,  10,  233),  and  expressing  the  results  in  terms  of  rise  of  tem- 
perature produced  by  substituting  an  equal  volume  of  water  for 
oil,  the  results  obtained  with  water  being  taken  as  100.  As  stated 
above,  the  Maumene  figure  is  usually  higher  the  higher  the  halogen 
absorption.  In  the  case  of  menhaden-oil,  however,  and  perhaps 
other  fish-oils,  the  Maumene  figure  is  higher  than  would  corre- 
spond with  its  iodine  or  bromine  absorption.  A  sample  having  a 
bromine  addition  figure  of  95,  as  against  linseed-oil,  which  would 


60  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

have  a  figure  usually  about  102,  would  give  a  Maumene  figure 
higher  than  that  of  the  linseed-oil.  Thomson  and  Ballantyne  find 
that  the  specific  rise  of  temperature  of  four  samples  of  linseed-oil 
which  they  examined  varied  from  270  to  349,  while  the  corre- 
sponding figure  for  a  sample  of  menhaden-oil  was  306.  Allen 
found  the  rise  of  temperature  with  sulphuric  acid  to  be  104  to  in 
in  the  case  of  linseed-oil,  and  126  in  the  case  of  menhaden-oil. 

It  will  be  seen  from  these  facts  that  if  an  oil  is  found  to  give 
a  distinctly  lower  bromine  addition  figure,  and  at  the  same  time  a 
Maumene  figure  distinctly  higher  than  specimens  of  pure  linseed- 
oil  tested  in  the  same  apparatus,  very  strong  evidence  of  the  pres- 
ence of  fish-oil  is  at  hand.  It  is  advisable  before  testing  a  sample 
of  oil  in  this  way  to  remove  from  the  oil  all  impurities,  as  far  as 
possible.  Volatile  oil  is  removed  with  comparative  ease.  Free 
rosin  can  be  largely  removed  by  repeated  treatment  with  moder- 
ately strong  alcohol,  and  subsequent  removal  of  any  alcohol  that 
may  remain  dissolved  in  the  oil  by  treatment  with  water  and  set- 
tling, keeping  the  vessel  hot.  Unsaponifiable  matter  and  soaps 
cannot  be  easily  removed,  but  in  extremely  important  cases  it 
might  be  advisable  to  prepare  a  quantity  of  the  fatty  acids  of  the 
sample  to  be  examined  by  saponifying  and  then  acidifying  the  oil, 
after  freeing  it  from  rosin,  as  far  as  possible.  Volatile  oil  could  be 
removed  during  the  saponification.  This  sample  of  fatty  acids 
could  then  be  tested  under  the  same  conditions  as  the  fatty  acids 
prepared  from  samples  of  pure  linseed-oil. 

Livache's  Test.  —  The  power  possessed  by  linseed-oil  in 
greater  measure  than  by  any  other  oil  to  absorb  oxygen  from 
the  air,  and  consequently  to  increase  in  weight,  is  measured 
by  Livache's  test  (Compt.  rend.,  1895,  I2°j  &42)-  *n  order  to 
hasten  the  absorption  of  oxygen  a  weighed  quantity  of  the  oil 
is  spread  out  in  a  thin  film  on  a  watch-glass,  and  mixed  with 
finely  divided  precipitated  metallic  lead.  At  the  end  of  each 
period  of  twelve  or  twenty-four  hours  the  mixture  is  weighed 
and  the  increase  in  weight  noted.  The  amount  of  oxygen 
absorbed  in  this  way  by  oils  is  roughly  proportional  to  the  absorp- 
tion of  bromine  and  iodine,  except  in  the  case  of  fish-oils.  Men- 


LINSEED-OIL.  6r 

haden-oil,  though  having  a  power  to  absorb  bromine  or  iodine 
but  slightly  inferior  to  that  of  linseed-oil,  falls  very  short  in  prac- 
tical drying  properties,  and  as  Livache's  test  comes  nearer  than 
any  other  to  an  actual  determination  of  the  real  drying  power 
of  an  oil,  menhaden-oil  is  indicated  by  a  proportionately  lower 
absorption  of  oxygen  than  of  that  of  linseed-oil,  than  the  bromine 
or  iodine  figures  of  the  sample.  Details  of  the  process  will  be 
found  in  Benedikt,  Allen,  and  Gill. 

Livache  found  linseed-oil  to  gain  14.3  per  cent  of  its  weight 
in  two  days,  while  Jean  (Monit.  Scient.,  15,  891)  found  menhaden- 
oil  to  gain  only  5.454  per  cent,  in  three  days. 

Thus  if  an  oil  have  a  bromine  addition  figure  (after  allow- 
ing for  the  effect  of  other  impurities  found)  that  is  only  slightly 
lower  than  that  of  linseed-oil,  but  absorbs  only  a  small  amount 
of  oxygen  by  Livache's  test,  there  is  good  proof  of  the  presence 
of  menhaden-oil. 

With  regard  to  other  adulterants  of  linseed-oil  the  test  does 
not  furnish  information  at  all  comparable  in  value  with  that 
obtained  by  determining  the  bromine  figures. 

Index  of  Refraction. — With  regard  to  the  index  of  refraction 
the  difference  between  the  figures  of  linseed-oil  and  of  its  adul- 
terants is  comparatively  small,  and  much  less  work  has  been 
done  in  this  direction  than  in  others.  The  following  figures- 
are  taken  from  several  authorities: 

Oil.  Refractive  Index. 

Linseed-oil i  .484  to  i  .488  at  15°  C. 

Cottonseed-oil i  .475  at  15°  C. 

Rosin-oil i .  535  to  i .  549  at  18°  C. 

Mineral  oil i .  438  to  i .  507 

Turpentine-oil i .  464  to  i .  474 

Rosin  (colophony) 1-548 

(1.478    at  20°  C. 

Corn-oil. \  0  _ 

(1.4765  at  15°  C. 

Fish-oil i  .480    at  15°  C. 

The  Action  on  Polarized  Light. — The  use  of  the  polariscope 
is  very  limited  in  testing  linseed-oil.     Little  has  been  done  with  it,. 


^2  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

and  its  value  in  this  connection  seems  to  be  confined  to  the  detec- 
tion of  rosin-oil,  which  is  dextro-rotatory.  Valenta  finds  its 
rotatory  power  to  be  3O°-4O°,  and  Demski  and  Morawski  find 
it  to  be  50°.  American  oil  of  turpentine  deviates  polarized  light 
to  the  right,  while  the  French  oil  of  turpentine  deviates  to  the 
left.  Mineral  oils  have  no  rotatory  power,  or  only  a  slight  one, 
and,  according  to  Bishop,  vegetable  oils,  with  the  exception  of 
sesame-oil,  rotate  to  the  left.  Therefore  a  right-handed  rotation 
in  a  sample  of  linseed-oil  is  indicative  of  rosin-oil. 

The  Best  Tests  to  Apply  in  Analyzing  Linseed-oils. — In 
examining  linseed-oil  for  adulteration  it  will  usually  be  found 
advisable  to  make  the  following  determinations: 

1.  Determine  the  specific  gravity  at   15°.  5  C.,   water  at  the 
same  temperature  being  taken  as  i.ooo.     This  should  be  between 
.931  and  .937  for  raw  oil,  and  between  .931  and  .950  for  boiled 
oil. 

2.  Determine  the  bromine  addition  figure  and   the  bromine 
substitution  figure.     The  former  should  be  between  100  and  no 
and  the  latter  should  not  be  higher  than  5,  though  it  may  rarely, 
in  a  pure  oil,  be  as  high  as  7,  probably  from  the  presence  of  an 
unusual  amount  of  non-fatty  matter  extracted  with  the  oil  from 
the  seed.     The  figures  to  be  expected  are  the  same  for  raw  oil 
and  boiled  oil  as  now  made. 

3.  Test  for  volatile  oil  by  the  odor  and  determine  the  amount 
present  by  distillation  with  steam.     There  should  be  none. 

4.  Determine    the    amount    of    non-volatile    unsaponifiable 
material.     There  should  be  less  than  2.5  per  cent,  in  either  raw 
or  boiled  oil. 

5.  Determine  the  acid  figure.     It  should  be  less  than  5  in 
either  raw  or  boiled  oil,  but  figures  as  high  as  7  may  indicate 
that  the  oil  is  old  rather  than  adulterated,  and  a  still  higher  figure 
may  prove  to   be   due  to   the   presence   of   mineral   acid  from 
refining. 

6.  Determine  the  Kcettstorfer  figure.     This  should  not  be  less 
than  187  in  the  case  of  raw  oil,  nor  less  than  186  in  the  case  of 
boiled  oil,  and  in  neither  case  should  be  higher  than  196. 


LINSEED-OIL.  63 

7.  If  the  appearance,  odor,  etc.,  of  an  oil  point  to  the  presence 
of  fish-oil,  apply  Maumene's  and  Livache's  tests. 

Adulteration  will  usually  be  indicated  by  more  than  one  test, 
and  if  abnormal  figures  are  obtained  by  one  process  pointing 
to  a  certain  kind  of  adulteration,  while  others,  which  would  also 
be  expected  to  be  abnormal,  are  not  so,  it  is  evident  that  some 
new  adulterant  is  to  be  sought  for,  or  that  the  oil  has,  perhaps, 
been  made  by  some  unusual  process. 

Detection  and  Determination  of  the  Several  Adulterants. — 
i.  Non-volatile  Mineral  Oil. — Indicated  by  low  bromine  absorp- 
tion, low  bromine  addition  figure,  low  Kcettstorfer  figure,  and 
low  specific  gravity.  Separated  and  weighed  together  with 
rosin-oil  as  unsaponifiable  matter,  and  separated  from  rosin- oil 
by  nitric  acid. 

2.  Benzine. — Indicated   by   odor,    low   specific   gravity,    low 
Kcettstorfer   and   bromine   addition   figures,  and   low    bromine 
absorption.     Separated    and    weighed    or    measured    together 
with  turpentine,  as  volatile  oil,  by  distillation  with  steam,  and 
separated  from  turpentine  with  fuming  nitric  acid. 

3.  Turpentine. — Indicated  by  odor,  low  specific  gravity,  low 
Kcettstorfer  figure,  and  high  bromine  absorption,  bromine  addi- 
tion figure,    and   bromine    substitution    figure.     Separated    and 
weighed  together  with  benzine  as  volatile  oil  by  distillation  with 
steam,  and  determined  by  difference,  after  treating  the  volatile  oil 
with  fuming  nitric  acid  and  hot  water. 

4.  Rosin-oil.  —  Indicated    by    high     specific     gravity,     low 
Kcettstorfer  figure,  often  high  acid  figure,  low  bromine  absorption 
and   bromine    addition    figure,    and   high   bromine    substitution 
figure.     Separated  and  weighed  together  with  non-volatile  mineral 
oil  as  unsaponifiable  matter,  and  determined  by  difference,  after 
treating  the  mixture  with  nitric  acid. 

5.  Rosin.—  Indicated  by  high  specific  gravity,  high  bromine 
absorption,  low  bromine  addition  figure,  high  bromine  substitution 
figure,  and  when  in  the  free  state  by  high  acid  figure.     Separated 
and  weighed  or  titrated  by  TwitchelPs  process  (J.  Soc.  Chem.  Ind., 
1891,  10,  804).     It  is  carried  out  by  treating  the  mixed  fatty  and 


TECHNOLOGY  OF  PAINT  AND    VARNISH. 


rosin  acids  obtained  by  acidifying  the  soap  solution  after  extrac- 
tion with  ether  in  the  determination  of  unsaponifiabie  matter,  in 
absolute  alcohol  solution,  with  hydrochloric  gas.  By  this  treat- 
ment the  fatty  acids  are  converted  into  ethyl  esters,  while  the  rosin 
acids  are  not.  The  products  of  the  reaction  are  boiled  with  water, 
the  mixed  fatty  acid  esters  and  rosin  separated  and  dissolved  in 
naphtha.  From  this  solution  the  rosin  is  extracted  by  potassium 
hydrate  solution.  The  rosin  soap  solution  is  treated  with  acid  and 
the  liberated  rosin  weighed.  For  full  details  Allen's  Comm.  Org. 
Anal.  (3d  ed.)  should  be  consulted. 

Cladding's  method,  Amer.  Chem.  J.,  3,  416,  formerly  much 
used  for  the  determination  of  rosin,  depends  upon  the  solubility  of 
silver  resinate  in  ether,  while  the  silver  salts  of  fatty  acids  are  in- 
soluble. 

6.  Menhaden-oil. — Indicated   by   a  bromine   addition   figure 
slightly  lower  than  that  of  linseed-oil,  but  a  higher  Maumene  figure 
and  a  very  much  lower  figure  by  Livache's  test.     Indicated  also 
by  characteristic  taste  and  odor. 

7.  Corn-  and  Cottonseed-oils. — Indicated  by  low  specific  gravity, 
low  bromine  absorption,  and  low  bromine  addition  figure. 

TABLE  SHOWING  THE  EFFECTS  OF  TEMPERATURE  UPON  THE  SPECIFIC  GRAVITY 

OF  LINSEED-OIL. 

(In  all  cases  water  at  15.5°  C.  taken  as  unity.) 


g 

A* 

4J 

44 

J 

o 

J 

1 

1 

O     **•' 
"°0 

OiL 

j| 

Oj 

5 

O   . 

IM  P< 

^°0 

^0 

4j 

£"? 

^d 

tC 

Si 

SiT 

M 

1 

|% 

g« 

11 

o< 

WD 

C°J, 

8? 

6" 

American  raw  linseed.  .  . 

S2 

.9336 

•9255 

.8736 

.  000650 

.000721 

.000711 

Raw  Calcutta  linseed 

.  000698 

Raw  American  linseed.  . 

02 

0^6 

02  CC 

.  000650 

Raw  American  linseed.  . 

9e 

.Q-24C 

.026"? 

.000656 

Boiled  American  linseed. 

j 
38 

yo  "O 
.9385 

y^wo 

.9297 

.  000707 

Boiled  American  linseed. 

onA^Sc  2 

Raw  American  linseed  .  . 

58 

•9327 

.]9293 

.8732 

."]  



.  000704 

Raw  American  linseed  .  . 

73 

•9332 

•9245 

.8731 

.000693 

.000714 

.  0007  i  i 

Boiled  American  linseed. 

72 

•9336 

.9258 

•8735 

.000625 

.000726 

.000714 

Menhaden  

71 

.9316 

.9235 

.8712 

.  000646 



.000716 

/ 

yo 

LINSEED-OIL. 


A  TABLE  SHOWING  THE  CORRECTION  FOR  TEMPERATURE  TO  BE  ADDED  TO  OR 
SUBTRACTED  FROM  THE  READINGS  OF  A  GLASS  HYDROMETER,  CORRECT  AT 
60°  F.  (i5°.5  C.)i  IMMERSED  IN  LINSEED-OIL,  FOR  EACH  DEGREE  FROM 
40°  F.  TO  85°  F. 

Calculated  from  the  results  obtained  in  determining  the  specific  gravity  of  sam- 
ples Nos.  88,  90,  92,  94,  and  95,  by  the  following  formula: 

Let  a  =  weight  of  oil  displaced  by  glass  plummet  at  15°. 5  C.; 
b  =  weight  of  oil  displaced  by  glass  plummet  at  28°. o  C.; 
c  =  weight  of  water  displaced  by  glass  plummet  at  15°. 5  C.; 
d  —  difference  in  apparent  gravity  of  hydrometer  for  i°. 

a-b 

=  d. 


28  -  15-5 

By  substituting  82°. 4  F.  and  60°  F.  for  28°  C.  in  the  formula  the  correction 
will  be  found  for  i°  F. 

Correction  for  i°  F.  =  .000361.     Correction  for  i°  C.  =  .000650. 


Ther- 
mometer 
Reading. 

Subtract. 

Ther- 
mometer 
Reading. 

Subtract. 

Ther- 
mometer 
Reading. 

Add. 

Ther- 
mometer 
Reading. 

Add. 

40  Fahr. 

.0072 

51  Fahr. 

.0032 

6  1  Fahr. 

.0004 

74  Fahr. 

.0051 

41 

.0069 

52 

.0029 

62 

.0007 

75 

.0054 

42 

.0065 

53 

.0025 

63 

.001  1 

76 

.0058 

43 

.0061 

54 

.0022 

64 

.0014 

77 

.0061 

44 

.0058 

55 

.0018 

65 

.0018 

78 

.0065 

45 

.0054 

56 

.0014 

66 

.0022 

79 

.0069 

46 

.0051 

57 

.001  1 

67 

.0025 

80 

.0072 

47 

.0047 

58 

.0007 

68 

.0029 

81 

.0076 

48 

.0043 

59 

.0004 

69 

.0032 

82 

.0079 

49 

.0040 

60 

.0000 

70 

.0036 

83 

.0083 

50 

.0036 

.0040 

84 

.0087 

72 

.0043 

85 

.0090 

73 

.0047 

66 


TECHNOLOGY   OF  PAINT  AND    VARNISH. 


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TECHNOLOGY  OF  PAINT  AND   VARNISH. 


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70  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

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CHAPTER  VI. 

MANUFACTURE  OF  VARNISH. 

THE  manufacture  of  varnish  is  carried  on  at  the  present  time 
as  a  definite  business,  independent  of  any  other,  and  is  in  fact 
subdivided  so  that  the  same  concern  does  not  make  or  try  to 
make  all  kinds  of  varnish.  In  fact  it  is  not  unusual  for  some  of 
the  smaller  and  more  rarely  some  of  the  larger  manufacturers  to 
purchase  varnishes,  either  for  direct  sale  or  for  use  in  making 
some  special  product,  from  other  makers  who  are  particularly 
successful  in  certain  lines  of  the  work.  The  greater  part  of  the 
varnish  now  used  is  made  from  linseed-oil  and  resins,  with  tur- 
pentine or  benzine  as  dilutent ;  but  most,  or  probably  all,  of  these 
makers  also  make  a  little  shellac  varnish,  which  is  a  spirit  varnish; 
and  they  all  make  damar  varnish,  which  is  a  solution  of  damarin 
spirits  of  turpentine.  On  the  other  hand,  they  almost  never  try 
to  make  the  more  unusual  spirit  varnishes,  or  those  which  have 
nitro-cellulose  as  a  base.  Some  of  the  spirit- varnish  makers, 
probably  most  of  them,  buy  small  quantities  of  oleo-resinous  var- 
nishes to  add  to  their  compounds,  and  not  a  few  paint-manufac- 
turers not  only  buy  what  varnish  they  use  as  an  ingredient  of 
their  paint,  but  do  a  considerable  business  as  varnish-merchants 
on  goods  made  for  them  and  put  up  in  special  packages  under 
their  own  label  and  seal. 

The  writer  of  this  disclaims  any  special  and  particular  knowl- 
edge of  what  is  done  by  English  and  European  varnish-makers, 
but  in  America  the  varnish-factory  equipment  may  thus  be  briefly 
described. 

Raw  Materials. — The  raw  materials  are  resins,  oil,  and  tur- 
pentine or  benzine.  To  these  may  be  added  the  necessary  driers, 

71 


72  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

lead  and  manganese  compounds;  and,  of  course,  fuel.  The  oil 
is  almost  invariably  bought  as  raw  oil,  i.e.,  oil  which  has  no 
addition  of  driers  and  has  not  been  highly  heated.  This  is  bought 
^  either  in  barrels  of  45  to  52  gallons  each,  usually  called  5o-gallon 
barrels,  in  which  case  the  buyer  pays  for  the  barrel,  which  he 
afterward  uses  to  ship  varnish  in,  or  in  large  casks  of  200  to  300 
gallons,  which  are  the  property  of  the  oil-merchant,  to  whom  they 
are  returned.  Oil  is  invariably  bought  from  the  manufacturers, 
as  no  varnish-maker  would  feel  confidence  in  oil  bought  from  a 
middleman,  and  is  usually  of  especially  fine  quality,  which  sells 
at  from  one  to  three  cents  a  gallon  above  the  market  price  of  ordi- 
nary pure  oil.  It  is  perfectly  clear  and  bright  from  having  been 
tanked  a  sufficient  time  and  filtered. 

Storage  and  Treatment  of  Oil. — When  this  oil  is  received,  part 
of  it  is  used  just  as  it  is  out  of  the  barrels,  but  the  most  of  that 
which  is  to  be  used  for  fine  varnishes  is  put  through  some  sort  of 
treatment  and  then  pumped  into  tanks  holding  one  to  three 
thousand  gallons,  in  a  storehouse,  where  it  can  be  held  at  a  tem- 
perature which  is  regulated  by  the  operator,  usually  90°  to  110° 
F.,  probably  never  exceeding  120°.  This  keeps  the  oil  rather 
thinly  fluid,  which  promotes  its  settling  and  clearing.  Each  var- 
nish-maker has  his  own  secret  methods  of  treating  oil,  which 
probably  are  all  about  alike.  One  of  the  most  common  is  to 
heat  the  oil  to  500°  or  550°  for  a  very  short  time.  This  seems 
to  char  certain  impurities  and  coloring-matter,  which  will  then 
settle  out.  Another  is  to  heat  with  a  very  small  amount  of  man- 
ganese, or  lead  oxides,  or  both:  not  enough  to  make  the  oil  dry 
much  more  rapidly,  but  a  very  little  seems  to  affect  the  quality  of 
the  oil  for  further  use.  A  comparatively  small  part  of  the  oil  is 
converted  into  "boiled  oil"  of  various  sorts.  The  varnish-maker 
does  not  make  boiled  oil  for  sale,  but  uses  several  different  kinds 
in  his  work.  All  these  oils  are  tanked  for  a  considerable  time, 
usually  several  months,  before  they  are  considered  to  be  in  the 
best  condition  for  use. 

Resins. — The  varnish-resins  are  stored  either  in  the  original 
packages  in  which  they  are  bought,  or  in  large  bins.  Usually  a 


s  # 


MANUFACTURE  OF    VARNISH.  73 

considerable  quantity  of  the  more  common  ones  is  kept  in  bins, 
but  the  less  common  in  the  original  packages.  It  is  the  practice 
of  the  varnish- makers  to  keep  a  large  stock  on  hand,  so  as  to  be 
able  to  take  advantage  of  the  market.  Probably  from  10  to  20 
per  cent,  of  the  entire  capital  of  the  business  is  invested  in  this 
way.  These  resins  come  from  all  parts  of  the  tropical  and 
south  temperate  zones  and  are  not  always  to  be  had  when  wanted. 
Oil,  on  the  contrary,  can  be  contracted  for  any  length  of  time 
ahead. 

Spirit  of  Turpentine. — Nearly  all  varnish-factories  contain 
one  or  more  tanks  of  turpentine.  This  is  stored  in  steel  tanks 
built  in  the  open  air  and  sometimes  hold  over  a  hundred  thousand 
gallons  of  spirit  of  turpentine.  These  tanks  are  closed,  except 
for  a  vent  to  admit  air  when  the  liquid  is  being  pumped  in  or 
out.  A  few  makers  have  also  tanks  for  benzine,  but  usually  this 
is  bought  from  day  to  day  and  no  tank,  or  only  a  small  one,  is 
necessary.  Other  supplies  are  kept  in  casks,  boxes,  or  small 
bins. 

Packages. — Varnish  is  sold  in  barrels,  half-barrels,  and  in 
tin  cans  ranging  in  size  from  lo-gallon  jacketed  cans  (cased 
with  wood)  and  5 -gallon  cans,  both  with  and  without  jackets, 
down  to  half-pints.  All  these,  except  the  jacketed  cans  and 
the  very  small  ones,  are  shipped  in  special  boxes  holding  from 
i  to  12  cans  of  a  size,  so  that  considerable  space  must  be  allowed 
for  empty  packages.  When  filled,  these  cans  are  closed,  not 
with  a  stopper,  but  with  a  piece  of  sheet  brass,  stamped  to  fit 
the  nozzle  of  the  can  and  made  tight  by  a  reamer,  a  little  device 
worked  by  hand  which  makes  an  absolutely  tight  closure.  In 
the  box  with  the  can  is  placed  a  wooden  stopper  or  a  metal  cap 
to  use  after  the  brass  cap  has  been  torn  off. 

Labels. — The  can,  of  course,  is  properly  labelled.  The 
stock  of  labels,  several  different  sizes  being  required  for  each 
kind  of  varnish,  frequently  amounts  in  cost  to  from  two  to  four 
thousand  dollars. 

The  buildings  are  heated  by  steam,  which  is  generated  in 
any  suitable  boiler.  Comparatively  little  power  is  used,  chiefly 


74 


TECHNOLOGY  OF  PAINT  AND    VARNISH. 


for  pumping  and  the  like,  but  coke  is  the  fuel  used  under  the 
varnish-kettles,  no  other  fuel  having  been  found  which  so  well 
satisfies  the  requirements. 

It  was  originally  the  custom  to  melt  the  resin  in  small  quan- 
tities; in  fact  the  business  was  formerly  a  small  business,  but  a 
good  many  years  ago  the  American  practice  was  to  melt  100 
pounds  at  a  time,  and  this  amount  was  so  convenient  for  compu- 
tations that  it  is  still  accepted  as  the  varnish-maker's  unit,  but 
the  present  general  practice  is  to  melt  125  pounds  at  a  time. 


VARNISH-KETTLE  AND  TRUCK. 

Varnish-kettle. — For  this  purpose  the  kettle  (see  illustration) 
is,  when  new,  about  36  inches  in  height  and  also  in  diameter, 
and  weighs  when  new  about  130  pounds.  The  bottom,  which 
is  riveted  on,  is  the  part  which  gives  out  first.  Then  the  strip 
containing  the  rivet-holes  is  cut  off  and  a  new  bottom  put  on,  thus 
decreasing  the  depth  of  the  kettle.  This  is  repeated  from  time 
to  time;  finally,  the  whole  of  the  kettle  becomes  too  thin  to  be 
safe,  and  when  sold  for  old  copper  the  weight  is  sometimes  not 
more  than  80  pounds.  The  fireplace  is  cleaned  out  and  the 
material  for  the  fire  prepared  before  leaving  at  night,  or  very 
early  in  the  morning.  The  fire  is  started  early,  and  the  fire-pit 
is  a  glowing  mass  of  coke  when  the  varnish-maker  is  ready  to 
begin  work.  The  resin  has  already  been  put  in  the  clean  kettle, 
which  sets  on  its  truck;  the  loose  cover  is  on,  and  the  kettle  is 
ready  to  put  on  the  fire,  which  comes  almost,  but  not  quite,  in 


FIREPLACE  IN  THE  OLDEST  AMERICAN  VARNISH-CHIMNEY. 

By  the  courtesy  of  Edward  Smith  &  Co. 


MANUFACTURE  OF   VARNISH.  75 

contact  with  the  bottom  of  the  kettle.  Through  a  hole  in  the 
cover  the  varnish-maker  inserts  a  slender  iron  rod,  set  in  a 
wooden  handle,  as  Theophilus  did  about  a  thousand  years  ago, 
and  stirs  the  melting  mass  of  resin. 

Melting  the  Resin. — When  all  the  lumps  are  gone,  and  the 
melted  gum,  a  little  of  which  adheres  to  the  stirring-rod  when 
the  operator  takes  it  out  for  inspection,  is  quite  liquid,  the  kettle 
is  drawn  off  the  fire.  By  this  time — it  is  about  half  an  hour 
from  the  beginning — from  10  to  25  per  cent.,  by  weight,  of  the 
resin  has  been  driven  off  in  the  form  of  a  pungent,  irritating, 
highly  inflammable  vapor.  To  keep  this  from  catching  fire  the 
cover  is  used,  and  the  free  escape  of  the  vapor  is  permitted  by 
the  little  chimney  in  the  middle  of  the  cover,  which  so  discharges 
the  issuing  stream  of  vapor  that  the  current  of  air  which  is  rush- 
ing up  the  chimney  carries  it  quickly  away  from  the  fire.  The 
escaping  vapor  causes  the  melted  part  of  the  resin  to  foam,  and 
if  this  appears  too  near  the  top,  the  operator  draws  the  kettle 
away  from  the  fire,  unless  he  can,  with  his  stirring-rod,  beat 
down  the  foam.  It  is  clearly  necessary  to  have  considerable 
space  in  the  kettle  over  the  resin,  and  formerly  the  kettles  were 
made  much  higher  in  proportion  to  their  width  than  now.  It 
is  not  common  to  use  a  thermometer  in  melting  resin  because 
the  essential  thing  is  not  to  reach  a  certain  temperature,  but  to 
melt  the  resin,  and  this  is  best  told  by  the  feeling  of  it  through 
the  stirring-rod,  by  the  experienced  operator.  In  the  laboratory, 
however,  where  the  lumps  of  resin  are  much  smaller,  the  thermom- 
eter is  necessary.  The  temperature  is  seldom  below  650°  F. 
when  the  melting  is  completed.  The  temperature  and  the 
percentage  of  loss  vary  greatly  with  different  resins. 

Adding  the  Oil.— When  the  resin  is  all  melted  and  the  kettle 
has  been  drawn  from  the  fire,  and  the  heat  subsided  a  little, 
and  the  foam  has  gone  down,  the  linseed-oil,  which  has  been 
made  ready  in  another  kettle,  is  slowly  added.  The  oil  is  by 
some,  perhaps  a  majority  of  makers,  previously  heated  to  about 
500°,  but  many  use  less  heat.  Some  heat  only  a  little  above 
212°  and  some  not  above  100°  F.  Of  course  if  only  a  little 


76  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

oil  is  added  its  temperature  has  not  much  effect  on  the  mass, 
but  it  is  common  to  have  the  oil  hot.  The  amount  of  oil  added 
is  variable,  according  to  the  kind  of  varnish  desired.  It  is  com- 
monly measured  in  United  States  gallons,  which  weigh  7j  pounds, 
but  the  varnish- maker  is  obliged  to  buy  his  oil  by  weight,  and  a 
gallon  is  then  said  to  weigh  yj  pounds.  The  price  is  always 
so  much  per  gallon,  but  a  gallon  of  linseed-oil,  when  buying  it 
from  the  oil-manufacturers,  is  a  conventional,  not  a  standard, 
gallon,  so  that  the  varnish- maker  has  to  buy  about  3  per  cent. 
more  than  he  sells.  Of  course  a  gallon  of  hot  oil  weighs  less 
than  a  gallon  of  cold  oil,  and  if  it  is  added  hot  allowance  must 
be  made  for  that,  but  usually,  if  it  is  hot,  it  was. previously  meas- 
ured cold  into  the  pot  in  which  it  was  heated. 

Cooking  the  Varnish. — As  soon  as  the  oil  has  been  added, 
which  is  done  gradually,  the  mixture  being  constantly  stirred,  the 
kettle  is  put  back  on  the  fire.  Although  the  mixture  appears  to 
be  a  complete  solution,  it  is  not  really  so  at  this  stage,  for  if  the 
mixture,  or  a  drop  of  it,  be  allowed  to  cool,  the  resinous  part  will 
separate,  making  the  drop  cloudy ;  and  the  common  rule  is  to  with- 
draw the  stirring-rod  from  time  to  time  and  let  a  drop  or  two  of 
the  mixture  fall  on  a  piece  of  glass,  where  it  cools  at  once  and 
shows  by  its  cloudiness  that  the  combination  has  not,  or  by  its 
clearness  that  it  has,  taken  place.  The  more  approved  practice 
now,  however,  is  to  keep  a  thermometer  in  the  liquid  and  heat  to 
a  certain  temperature,  previously  determined  as  the  best  for  the 
particular  varnish  which  is  being  made,  for  a  certain  length  of 
time.  This  temperature,  roughly  speaking,  is  not  very  far  from 
500°  F.,  but  not  unfrequently  it  is  found  best  to  make  the  heat 
increase  and  diminish  from  time  to  time,  according  to  a  tempera- 
ture curve  which  is  established  for  a  given  mixture.  In  general 
it  may  be  said  that  varnishes  containing  a  large  proportion  of  oil 
require  more  cooking  than  those  using  a  small  amount.  A  30- 
gallon  varnish,  for  example,  may  be  cooked  six  or  eight  hours,  or 
more,  while  a  lo-gallon  one  will  be  done  in  an  hour  or  two,  and 
where  a  very  small  percentage  of  oil  is  used  the  mixture  is  only 
heated  enough  to  be  sure  it  will  not  separate  on  cooling.  One 


MANUFACTURE  OF   VARNISH.  77 

effect  of  cooking  is  to  make  the  varnish  heavy  in  body,  or,  as  the 
English  say,  " stout";  that  is,  it  increases  its  viscidity  or  viscosity, 
and  the  longer  it  is  cooked  the  more  turpentine  will  be  required 
to  thin  it  to  the  conventional  standard  of  viscosity  which  is  desired 
in  a  finished  varnish. 

Undercooking. — If  it  is  cooked  but  a  little  it  will  take  less 
than  the  normal  amount  of  turpentine;  hence  a  gallon  of  such 
varnish  will  contain  a  large  proportion  of  non- volatile  matter,  and 
when  it  is  spread  on  a  surface  it  will  dry  to  a  film  of  more  than 
the  usual  thickness,  and  this,  in  turn,  requires  more  oxygen  to  dry 
it,  and  hence  a  longer  time,  than  a  thinner  film. 

Overcooking. — Conversely,  a  varnish  which  is  overcooked 
takes  a  large  amount  of  turpentine,  a  larger  percentage  of  the 
film  evaporates,  the  film  is  thinner,  and  it  dries  more  quickly. 
Looking  at  it  in  another  way,  since  turpentine  is  less  costly  than 
the  finished  product,  the  more  the  varnish  is  cooked  and  the  more 
turpentine  is  added  the  less  is  the  cost  per  gallon;  but  an  over- 
cooked varnish  is  liable  to  be  spoiled  by  carrying  the  cooking 
process  too  far,  and  hence  the  risk  makes  such  a  varnish,  in  the 
long  run,  more  costly  than  it  otherwise  would  be.  From  a  stand- 
point of  durability,  the  varnish  which  is  overcooked  leaves  a 
thinner  film,  which  is  on  that  account  less  durable,  than  one  less, 
cooked;  but  if  it  is  undercooked  the  oil  and  resin  are  not  very 
thoroughly  combined,  and  the  film  perishes  because  its  ingredi- 
ents separate  when  exposed  to  the  air  and  sunlight.  Since  var- 
nishes continually  grow  darker  in  color  by  cooking,  the  varnishes 
which  are  undercooked  are  paler  in  color,  and  on  that  account 
fetch  a  higher  price,  but  obviously  are  not  to  be  compared  in  real 
value  and  durability  with  a  varnish  of  the  same  color  made  of 
more  costly  materials,  that  is,  with  carefully  bleached  oil  and 
pure,  clean,  pale,  hard  resins  which  do  not  discolor  so  much  in 
melting,  and  more  thoroughly  combined  by  long  and  judicious 
cooking.  Most  of  these  considerations  apply  also  to  melting  the 
resin.  When  this  is  nearly  melted  and  the  full  heat  is  on,  it 
darkens  rapidly  every  minute  it  is  kept  over  the  fire ;  but  the  un- 
decomposed  resin  is  not  soluble  in  oil,  and  if  the  process  is  not 


78  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

carried  far  enough  the  result  will  be,  in  extreme  cases,  that  when 
the  oil  is  added  the  varnish  so  made  will  be  a  jelly,  which  must 
be  thrown  away;  and  if  the  result  is  not  so  bad  as  that,  the  varnish 
thus  made,  while  pale  in  color,  will  easily  suffer  decomposition. 
On  the  other  hand,  if  the  melted  resin  is  heated  too  long  it  be- 
comes very  dark  in  color  and  is  less  valuable  in  other  respects 
also.  As  a  rule,  when  we  consider  the  different  grades  of  a  given 
kind  of  resin,  Kauri  for  instance,  we  find  that  the  very  pale  sorts 
are  a  softer  resin  than  the  darker  pieces.  These  soft  resins  take 
on  color  more  rapidly  than  the  hard  ones,  hence  the  tendency  is 
to  melt  them  at  a  lower  temperature,  and  the  resulting  varnish, 
while  pale  in  color,  is  less  durable  than  that  made  of  the  darker 
resins. 

Different  Qualities  of  Resins. — But  the  cheaper  grades,  that 
is,  when  we  get  below  the  normal  or  standard  grade,  are  dark  not 
only  because  of  the  natural  color  of  the  resin,  but  because  it  con- 
tains impurities  of  various  sorts,  dirt  which,  in  most  cases,  settles 
out  and  does  not  injure  the  varnish  much,  except  in  color.  Some 
of  these  moderately  cheap,  very  dark-colored  varnishes  are  of  the 
most  excellent  quality  in  everything  but  color,  and  in  many  cases 
this  is  not  an  objection.  For  instance,  a  varnish  for  mahogany 
or  any  such  dark  wood  ought  to  be  dark  in  color.  The  dry  film 
is  like  red-brown  glass,  perfectly  clear  and  transparent,  and  im- 
parts a  rich  effect  whose  brilliancy  cannot  be  attained  in  any 
other  way.  But  if  a  pale  varnish  of  fine  quality  is  desired,  it  is 
necessary  to  select  a  pale  hard  resin  and  one  which  discolors  as 
little  as  possible  in  melting.  These  are  rare  and  costly.  Some 
of  the  finer  sorts  cost  as  much  as  75  cents  per  pound.  If  such  a 
resin  does  not  make  a  sufficiently  pale  product,  the  maker  pro- 
ceeds to  pick  out  the  very  best  pieces  from  this  most  valuable 
resin.  It  may  be  necessary  to  pick  over  a  thousand  pounds  to 
get  a  hundred  pounds,  enough  for  one  melt,  of  these  select  pieces. 
This  hand-picked  resin  not  only  costs  the  original  75  ce§ts  a 
pound,  plus  the  cost  of  skilled  labor  for  picking  over  the  thousand 
pounds,  but  the  residuary  900  pounds  has  by  this  process  been 
graded  down  to,  let  us  say,  6ocent  resin,  a  loss  of  15  cents  a 


MANUFACTURE  OF   VARNISH.  79 

pound  on  900  pounds,  or  $.1.35.  If  the  labor  cost  $15,  the 
cost  of  this  hundred  pounds  of  resin  would  be  $225,  or  $2.25  a 
pound.  Clearly,  a  varnish  made  of  such  a  resin  will  be  costly. 
It  will,  therefore,  be  used  only  indoors,  that  is,  for  objects  not 
exposed  to  the  weather.  Therefore,  it  will  be  made  with  a 
rather  small  proportion  of  oil,  and  since  oil  is  cheap  compared 
with  such  a  resin,  it  will  have  its  cost  reduced  as  little  as  possible 
in  this  way.  It  is  impossible  to  make,  even  if  we  could  sell, 
much  of  this  sort  of  varnish,  which  must,  therefore,  have  a 
special  small  tank  for  itself,  and  it  will  naturally  demand  the 
very  best  and  highest-priced  labor  in  the  factory  at  every  step 
of  its  making  and  handling  until  it  gets  out  of  the  shipping- 
room. 

Very  Costly  Varnish. — The  unavoidable  waste  in  handling  a 
material  which  is  sold  in  such  small  quantities  is  considerable, 
and  it  is  easily  seen  that  it  is  quite  practicable  to  make  a  varnish 
which  is  easily  worth,  from  a  factory  standpoint,  at  least  twenty 
dollars  a  gallon  and  which  may  be  absolutely  no  better  in  any 
respect  except  color  than  another  made  of  similar  but  less  costly 
materials  and  sold  for  one-quarter  or  one-fifth  the  price.  On  the 
other  hand,  if  a  man  builds  a  yacht  at  a  cost  of  half  a  million 
dollars  and  wishes  to  have  in  it  his  wife's  boudoir  varnished  with 
such  a  material,  the  cost  does  not,  and  ought  not,  to  stand  in  the 
way. 

It  has  been  said  that  there  is  danger,  if  the  resin  is  not 
thoroughly  melted  and  decomposed,  or  if  the  mixture  of  resin 
and  oil  is  not  sufficiently  heated  for  a  long  enough  time,  that 
the  same  will  be  spoiled.  It  should  further  be  said  that  if  the 
compound  of  resin  and  oil  be  overcooked  it  is  liable  to  turn  to 
a  viscid,  insoluble,  infusible  mass,  and  this  is  the  more  likely 
to  occur  if  the  resin  was  not  in  the  first  place  properly  melted, 
and  is  more  likely  to  take  place  with,  varnishes  containing  little 
oil  than  with  those  which  have  more.  It  may  be  remarked 
here  that  varnishes  containing  little  oil  are  sometimes  spoken 
of  as  "short"  varnishes,  and  those  with  a  large  amount  of  oil 
as  "long"  or  sometimes  "rich,"  but  the  terms  "quick"  and 


8o  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

"slow"  refer  to  the  rate  of  drying  and  not  to  the  composition. 
It  is  also  worthy  of  note  that  in  all  varnish-factories  a  certain 
amount — sometimes  a  pretty  large  one — of  common  rosin,  or 
colophony,  is  used,  and  this  is  always  called  rosin;  and  partly 
because  of  the  similarity  of  this  word  to  resin,  partly  because 
from  time  immemorial  all  resins  have  been  commercially  spoken 
of  as  "gums,"  the  word  resin  is  seldom  heard  in  a  varnish -factory, 
all  the  true  varnish-resins  being  called  "gums." 

"  Gum." — But  rosin  is  never  called  a  gum.  When  the  oil 
and  resin  have  been  properly  cooked  the  kettle  is  withdrawn 
from  the  fire  and  taken  to  a  sufficient  distance,  usually  into  a 
shed  or  well- ventilated  room,  from  which  it  is  impossible  that 
the  vapors  about  to  be  generated  should  reach  the  fire  and  thus 
cause  a  conflagration;  a  quantity  of  spirit  of  turpentine,  which 
has  been  measured  out  into  a  special  receptacle,  is  added,  being 
allowed  to  run  in  in  a  small  stream,  while  the  attendant  vigorously 
stirs  the  liquid  to  promote  the  solution. 

Thinning  Down  with  Turpentine. — Although  the  oil  and 
resin  compound  has  previously  been  allowed  to  cool  somewhat, 
its  temperature  is  still  a  little  above  the  boiling-point  of  the  tur- 
pentine, and  until  the  whole  has  been  sufficiently  cooled  by  the 
addition  of  cold  turpentine,  part  of  the  latter  is  converted  into 
vapor  and  flows  over  the  edge  of  the  kettle  in  the  form  of  a  gas, 
highly  inflammable,  and  indeed  explosive  if  ignited.  If  benzine 
is  used  instead  of  turpentine,  as  it  is  for  making  cheap  varnishes, 
this  danger  is  greatly  increased,  and  most  varnish  fires  occur 
from  this  cause.  Fires  do  indeed  sometimes,  but  rarely,  occur 
in  the  chimney  where  the  oil  and  resin  only  are  used,  but  these 
are  easily  and  quickly  put  out  by  smothering  them,  covering 
the  kettle  with  wet  burlap  or  other  wet  cloths,  a  supply  of  which 
is  constantly  on  hand.  Sooty  matter  sometimes  collects  on 
the  bottom  of  the  kettle,  and  in  this  sparks  of  fire  are  preserved 
for  a  considerable  time,  and  the  attendant  should  most  care- 
fully see  that  no  such  thing  is  allowed  to  cause  a  fire,  which  is 
not  only  destructive  to  the  part  of  the  factory  where  it  is,  but 
is  also  exceedingly  dangerous  to  the  workman  who  is  stirring  in 


MANUFACTURE  OF   VARNISH.  8l 

the  turpentine  or  benzine,,  Fires  are  avoidable  if  proper  care 
is  taken.  In  the  factory  with  which  the  writer  is  connected 
a  fire  of  this  sort  occurred  many  years  ago,  when  benzine  was 
first  introduced  and  before  it  was  known  that  it  was  more  dan- 
gerous than  turpentine;  but  that  one  fire  is  the  only  serious  one 
in  this  factory  in  seventy-five  years.  The  most  common  cause 
of  varnish  fires  is  that  the  thinning-down  shed  is  not  far  enough 
away  or  not  perfectly  separated  from  the  fireplace  where  the 
varnish  is  made.  When  making  cheap  rosin  varnishes,  more- 
over, it  is  common  practice  to  make  a  batch  of  varnish,  get  it 
thinned  down  and  pumped  out  of  the  kettle  all  within  an  hour, 
and  sometimes  considerably  within  the  hour.  Such  haste,  so 
different  from  the  more  dignified  and  deliberate  proceedings 
which  distinguish  the  making  of  high-class  goods,  is  a  contribu- 
tory cause  of  much  importance. 

If  the  varnish  is  one  containing  a  large  proportion  of  linseed- 
oil,  the  compound  of  oil  and  resin  will  be  much  more  fluid  than 
if  a  small  amount  of  oil  is  used,  and  consequently  a  smaller  propor- 
tion of  turpentine  will  be  needed  than  is  used  with  the  more 
viscid  compound  containing  a  small  proportion  of  oil.  Of 
course  it  is  possible  to  overcook  a  "long"  varnish  so  as  to  make 
it  take  more  than  its  normal  percentage  of  turpentine,  but  since 
this  is  rarely  done  we  have  some  indication  of  the  proportion 
of  resin  and  oil  when  we  determine  the  percentage  of  turpentine, 
or  rather  of  volatile  liquid  corresponding  to  turpentine,  which 
fortunately  may  be  easily  done.  Varnishes  made  with  8  gallons 
of  oil  to  ico  pounds  of  resin  have  about  25  gallons  of  turpentine 
added,  those  containing  30  gallons  of  oil  have  about  32  of  turpen- 
tine, and  intermediate  ones  are  somewhat  in  proportion. 

Turpentine  Better  than  Benzine. — The  question  will  naturally 
arise,  is  turpentine,  which  costs  three  to  five  times  as  much  as 
benzine,  any  better  than  the  latter?  In  most  cases  it  is,  for 
several  reasons.  One  of  these  is  that  it  is  much  less  rapidly 
evaporated.  There  is  much  more  attraction  between  the  oleo- 
resinous  compound  and  turpentine  than  between  it  and  benzine, 
and  for  that  reason  turpentine  goes  off  more  slowly,  and  benzine 


82  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

dissolves  in  the  air  by  diffusion  far  more  rapidly  than  turpentine, 
and  this  has  a  like  effect.  It  is  desirable  to  have  the  volatile 
ingredient  of  varnish  pass  off  somewhat  slowly,  especially  at 
first,  for  when  the  varnish  is  spread  with  a  brush  it  is  impossible 
to  avoid  putting  it  on  with  slight  irregularity,  and  the  brush- 
marks  thus  made  will  disappear  if  the  varnish  retains  its  liquid 
condition  for  some  time,  as  is  the  case  if  turpentine  is  the  solvent. 
The  little  ridges  of  liquid  varnish  flow  out  and  level  up  the  hollows 
and  the  whole  surface  becomes  smooth.  Such  varnish  is  said 
to  have  good  flowing  quality.  If  made  with  benzine,  the  latter 
evaporates  almost  at  once  and  the  varnish  takes  its  initial  set 
before  the  ridges  have  disappeared;  the  surface  then  dries  with 
these  imperfections,  and  the  finished  surface  shows  these  brush- 
marks.  These  may  be  seen  in  any  furniture -store  on  low-priced 
furniture.  Good  flowing  quality  is  also  helped  by  other  things; 
the  composition,  method  of  manufacture,  and  age  of  the  varnish 
have  their  influence,  but  the  presence  of  either  turpentine  or 
benzine  is  the  most  important  single  factor. 

Oxidation  of  Turpentine. — Another  peculiarity  of  turpentine 
is  that  it  never  completely  evaporates.  A  small  portion  of  it 
remains  behind  as  an  elastic  resinous  substance,  which  is  con- 
sidered a  desirable  ingredient  in  varnish.  Benzine  evaporates 
completely.  This  thickening  of  turpentine  is  due  to  a  process 
of  oxidation,  and  there  is  no  doubt  in  the  mind  of  the  writer  that 
turpentine  has  some  effect  as  a  drier,  acting  as  lead  and  manganese 
compounds  do,  by  passing  oxygen  on  from  the  air  to  the  oleo- 
resinous  compound.  It  is  possible  that  a  turpentine  varnish 
dries  through  more  quickly  than  a  similar  varnish  made  with 
benzine,  notwithstanding  the  slow  setting  of  the  former. 

Factory  Nomenclature. — If  10  gallons  of  oil  is  added  to  the 
melted  mass,  weighing,  let  us  say,  95  pounds,  which  results  from 
melting  125  pounds  of  resin,  the  resulting  varnish  is  said  to  be  an 
8-gallon  varnish,  because.it  contains  8  gallons  of  oil  to  every  100 
pounds  of  resin  originally  taken.  Similarly,  25  gallons  of  oil 
would  make  a  2o-gallon  varnish,  and  so  on,  the  varnishes  being 
designated  by  the  proportion  of  pil  to  the  hundred  pounds  of  un- 


MANUFACTURE  OF   VARNISH.  83 

melted  resin,  and  nothing  is  said  about  the  turpentine  which  is> 
to  some  extent,  a  variable  quantity.  Of  course  this  is  purely  a 
factory  nomenclature.  The  purchaser  knows  the  varnishes  he 
buys  by  certain  descriptive  or  trade  names,  and,  as  in  every  other 
business,  a  name  which  takes  the  public  fancy  is  very  valuable. 
Further,  the  varnish  as  it  comes  out  of  the  kettle  is  not  usually 
of  the  same  composition  as  any  varnish  sold,  because,  in  order  to 
get  certain  qualities,  it  is  necessary  to  mix  varnishes  made  in  dif- 
ferent ways  and  of  different  resins.  It  will  be  obvious  that  if  the 
maker  has,  for  example,  three  tanks  of  lo-gallon  varnishes,  made 
respectively  of  Zanzibar,  Kauri,  and  Manila  resin,  and  also  three 
tanks  of  3o-gallon  varnishes  made  from  the  same  resins,  he  is  in  a 
position  to  supply  nine  different  kinds  of  2O-gallon  varnish,  each 
differing  from  the  others  in  certain  properties  peculiar  to  each 
mixture,  and  also  in  price,  making  each  of  these  mixtures  from, 
two  tanks,  and  an  indefinite  number  by  mixing  them  in  a  more 
intricate  manner. 

Art  of  Mixing  Varnishes. — It  would  be  indeed  remarkable  if 
some  of  these  20-gallon  mixtures  were  not  better  for  some  special 
purpose,  or  even  for  general  use,  than  any  possible  20-gallon 
varnish,  made  from  a  single  resin,  just  as  it  comes  from  the  kettle* 
It  will  also  be  obvious  that  an  indefinite  number  of  12-,  15-,  18-, 
22-,  25-,  and  28-gallon  varnishes  may  be  made  from  these  same 
tanks,  and  if ,  in  addition,  the  manufacturer  has  a  set  of  tanks  of 
8-,  1 6-,  and  20-gallon  varnishes,  each  set  representing,  say,  these 
same  three  resins,  the  number  of  possible  combinations  passes 
imagination.  It  is  to  be  further  remembered  that  varnishes  are 
made  with  as  little  as  3  gallons  of  oil  and  as  high  as  60;  that  the 
'more  important  resins  are  sold  in  from  two  to  ten  grades,  and 
that  the  number  of  these  resins  is  very  great  and  is  constantly 
increasing.  It  will  be  seen  that  a  knowledge  of  the  qualities  of  the 
various  varnishes,  and  especially  of  their  effect  in  mixtures,  is  of 
as  much  importance  as  knowing  how  to  manipulate  the  materials 
in  the  kettle,  and  the  expert,  to  be  an  expert,  must  be  intimately 
and  practically  acquainted  with  the  use  to  which  the  varnish  is 
to  be  put  and  the  way  in  which  it  is  necessary  to  apply  it,  and  how 


84  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

these  uses  and  conditions  vary.  He  should,  therefore,  have  as 
the  simplest  foundation  a  good  working  knowledge  of  the  furni- 
ture trade,  of  wagon  and  carriage  building  of  railway  engines  and 
coaches,  of  ship  and  boat  construction,  and  of  house  painting  and 
decoration.  To  these  he  may  add  the  lesser  trades  and  special- 
ties, from  the  making  of  oilcloth  to  the  japanning  of  hooks  and 
eyes,  as  far  as  his  natural  abilities  and  acquired  opportunities 
may  allow. 

In  view  of  all  the  foregoing  facts,  the  proposition  that  the  art 
of  varnish-making  offers  an  opportunity  for  the  continual  activity 
of  an  ingenious  and  receptive  mind,  for  an  indefinite  period,  is 
confidently  submitted  to  the  acute  perceptions  of  the  candid 
reader. 


CHAPTER  VH. 

TUNG-OIL. 

TUNG-OIL,  or  Chinese  wood-oil,  is  a  remarkable  oil  which  sur- 
passes linseed  in  its  rapidity  of  drying;  it  is  obtained  from  the 
seeds  of  a  tree  known  to  botanists  as  the  Aleurites  cor  data,  much 
resembling  the  ornamental  tree  known  to  us  as  Paulownia 
japonica;  the  seeds  resemble  chestnuts  and  contain  somewhat 
more  than  half  their  weight  of  oil,  about  four-fifths  of  which  oil 
is  obtained  by  grinding  the  seeds  and  pressing,  very  much  as  lin- 
seed and  other  vegetable  oils  are  made.  The  nut  is  said  to  be 
poisonous  if  eaten;  but  it  is  not  reported  that  the  oil  is  so.  The 
oil  has  a  peculiar  odor,  resembling  that  of  rancid  grease  obtained 
from  bacon;  it  is  yellow  in  color,  darker  than  linseed,  and  is, 
when  fresh,  turbid;  this  turbid  oil  is  said  to  dry  better  than  it 
does  after  it  has  been  cleared.  When  spread  on  glass  (or  other 
non-absorbent  surface)  it  dries  "flat,"  that  is,  with  a  rough  sur- 
face, not  glossy,  and  makes  an  opaque  white  film.  Linseed-oil, 
after  it  has  taken  its  initial  set,  dries  from  the  outer  surface ;  but 
it  is  commonly  said  that  tung-oil  dries  throughout  at  the  same  rate. 
As  the  oxygen  is  derived  from  the  surface,  this  statement  is  no 
doubt  only  approximately  true;  but  it  dries  more  rapidly  and 
uniformly  than  linseed. 

The  next  most  remarkable  quality  of  tung-oil  is  that  if  it  is 
heated  to  about  400°  F.  it  coagulates;  it  does  not  break  like 
linseed,  but  apparently  the  whole  mass  of  the  oil  is  converted 
into  a  polymeric  modification,  and  is  a  jelly,  insoluble  in  all  the 
ordinary  solvents;  on  this  account  great  care  must  be  taken  in 
"heating  it.  It  may  sometimes  be  heated  to  about  500°  F.  for  a 

85 


86  TECHNOLOGY  OF  PAINT  AND    VARNISH, 

few  minutes;  but  prolonged  heating  to  400°  F.  is  likely  to  cause 
it  to  coagulate  into  a  gelatinous  solid  free  from  a  greasy  feeling. 

Tung-oil  seems  to  be  rather  more  repellent  to  water  than  lin- 
seed; but  the  writer  has  had  very  little  practical  experience  with 
it;  the  varnishes  made  with  it  have  not  seemed  to  be  as  reliable 
as  those  made  with  linseed-oil;  they  are  liable  to  undergo  a  de- 
composition while  standing  in  the  tank  or  can,  in  many  cases. 

There  is  a  considerable  amount  of  this  oil  used  in  the  United 
States;  the  most  of  it  seems  to  be  purchased  by  makers  of  rosin 
varnishes,  some  of  whom  must -have  successful  methods  of  using 
it.  It  is  more  costly  than  linseed. 

Its  specific  gravity  averages  about  .938,  varying  from  .936  to 
.944;  its  saponification  number  is  about  192.5,  varying  from  191 
to  197;  its  iodine  number  is  160,  varying  from  155  to  165. 

It  is  said  by  some  authorities  that  the  gelatinization  of  this 
oil  by  heat  is  accompanied  by  a  large  absorption  of  oxygen;  by 
others  that  it  is  not  so,  but  is  a  polymeric  change.  The  latter 
seems  the  more  likely. 

It  derives  its  name  of  wood-oil  from  the  fact  that  it  is  used 
as  a  protective  coating  for  wood  in  China,  being  used  as  a  sort 
of  varnish.  It  combines  readily  with  lead  and  manganese  oxides 
to  form  driers,  and  a  certain  proportion  of  lead  in  combination 
is  said  to  make  the  film  glossy  and  transparent  instead  of  fiat  and 
opaque. 


i?*¥.r 

&trEs«f  ;.'    /•    <?t'^  ..    .v^y 


CHAPTER  Vin. 

JAPANS  AND  DRIERS. 

THESE  terms,  japans  and  driers,  are  perhaps  the  most  in- 
definite used  in  the  varnish  and  paint  business.  It  is  commonly 
known  that  the  Japanese  and  Chinese  make  varnishes  of  peculiar 
character,  with  which  they  make  a  beautiful  glossy  coating  on 
articles  of  various  kinds;  and  at  one  time,  about  the  middle 
of  the  eighteenth  century,  imitations  of  this  varnish,  or  var- 
nishes made  to  imitate,  rather  remotely,  the  surfaces  of  this 
sort,  were  called  Japan  varnish.  One  way  of  doing  this  work 
was  to  put  the  varnished  article  into  a  hot  oven  and  dry  the  coat- 
ing from  a  melted  condition,  and  the  kind  of  varnish  useful  for 
this  treatment  came  to  be  called  japan,  and  the  process  japan- 
ning. This  is  one  kind  of  japan  made  and  used  largely  at  the 
present  day;  but  it  is  now  almost  always  spoken  of  as  baking- 
japan.  The  term  japanning  always  refers  to  the  use  of  this 
article.  Another  kind  of  varnish  was  also  used  to  imitate  this 
effect,  and  this  was  a  thin  liquid,  which  dried  very  rapidly  and 
to  a  hard  surface.  It  was  possible  to  apply  many  coats  of  this, 
which  was  made  to  dry  very  quicky  by  being  highly  charged 
with  lead  compounds.  From  this  kind  of  varnish  the  term  japan 
has  come  to  be  applied  to  a  liquid  the  most  conspicuous  property 
of  which  is  its  capacity  of  exceedingly  rapid  oxidation,  brought 
about  by  loading  it  to  saturation  with  lead  and  manganese  com- 
pounds. These  two  kinds  of  japan  are  therefore  as  unlike  as 
possible  in  appearance,  composition,  and  use;  and  they  agree 
only  in  perpetuating  the  record  of  failure  of  the  European  varnish- 
maker  to  successfully  imitate  the  products  of  the  country  whose 
name  they  bear. 

87 


88  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

The  subject  of  baking-japans  will  be  reserved  for  a  later 
chapter;  the  drying- japans  and  the  driers  form  a  class  by  them- 
selves. 

Driers. — It  has  already  been  explained  that  lead  and  man- 
ganese compounds  of  linseed-oil  impart  to  the  oil  or  varnish 
in  which  they  are  dissolved  the  property  of  more  rapid  oxidation; 
it  may  now  be  added  that  lead  and  manganese  combine  readily 
with  common  rosin,  or  colophony,  to  form  resinates,  and  that 
these  act  in  the  same  way  when  dissolved  in  oil  or  varnish,  and 
that  all  such  preparations  are  called  driers.  These  compounds 
are  made  by  heating  the  oxides  of  the  metals  with  the  oil  or 
resin,  and  since  this  compound,  which  is  liquid  when  hot,  is  a 
solid  cake  when  cold,  the  melted  mass  is  dissolved  in  turpentine 
or  benzine,  usually  to  a  rather  thin  fluid.  Various  resins  are 
sometimes  put  into  the  kettle  with  the  oil  and  the  oxides,  shellac 
especially  being  used  in  this  way,  and  either  the  lead  and  manga- 
nese combine  to  some  extent  with  the  resins  and  make  an  oil- 
soluble  compound,  or,  more  likely,  the  resins — which,  not  having 
been  previously  melted,  are  insoluble  in  oil — are  soluble  in  the 
compound  of  oil  with  lead  and  manganese;  at  any  rate,  a  com- 
pound is  made  which  when  diluted  with  turpentine  or  benzine 
possesses  some  of  the  qualities  of  varnish  and  not  only  dries 
quickly  itself,  but  imparts  that  property  to  any  paint  or  varnish 
to  which  it  is  added,  and  these  varnish-like  driers  are  called 
japans. 

Japans. — Probably  the  original  difference,  if  there  ever  was 
an  original  difference,  between  japans  and  driers  lay  in  this, 
that  a  varnish  resin  was  an  ingredient  of  a  japan,  but  the  terms 
have  now  become  so  confused  that  any  sharp  separation  by 
definition  is  impossible.  Still  there  are  substances  to  which 
the  name  of  japan  is  given  which  no  one  calls  driers,  and  there 
are  driers  which  no  one  calls  japans. 

The  action  of  driers  may  be  best  understood  by  first  describ- 
ing a  different  but  analogous  process,  the  formation  of  white 
lead  or  carbonate  of  lead  from  metallic  lead  and  the  carbonic 
acid  of  the  air.  Carbonic  acid  readily  attacks  metallic  lead, 


JAPANS  AND  DRIERS.  89 

but  a  very  thin  film  is  formed  of  lead  carbonate  which  protects 
the  metal  beneath.  The  sheet  of  metallic  lead  is,  therefore, 
put,  loosely  rolled,  in  a  jar  with  a  very  small  quantity  of  acetic 
acid.  This  acid  eagerly  attacks  the  lead,  forming  lead  acetate. 
Carbonic  acid  is  a  stronger  acid  than  acetic  and  it,  in  turn,  attacks 
the  lead  acetate,  forming  lead  carbonate,  and  the  acetic  acid 
is  set  free  to  attack  a  fresh  quantity  of  lead,  and  this  process  goes 
on  until  all  the  lead  is  converted.  At  the  close  we  should  theoret- 
ically have  all  the  acetic  acid  we  began  with;  in  practice  some 
of  it  evaporates. 

Theory  of  Driers. — Driers  act  in  a  similar  manner,  taking 
up  oxygen  from  the  air  and  giving  it  up  to  the  oil.  These  driers 
are  compounds  of  lead  and  manganese,  in  solution  in  the  oil; 
these  metals  have  the  power  of  forming  two  sets  of  oxygenated 
compounds,  the  peroxidized  ones  having  twice  as  much  oxygen 
as  the  others.  When  in  linseed-oil  they  give  up  half  their  oxygen 
to  the  oil;  then,  being  exposed  to  the  air,  they  absorb  a  fresh 
equivalent  of  oxygen,  which  again  the  oil  takes  from  them;  in 
this  way  they  act  as  carriers  of  oxygen  from  the  air  to  the  oil, 
acting,  of  course,  only  when  the  oil  is  spread  out  in  a  film  and 
exposed  to  the  air.  Since  the  oil  is  thus  converted  into  a  solid 
dry  substance,  these  agents  are  called  driers. 

Boiled  Oil. — When  oil  is  treated  with  a  small  amount,  usually 
about  2  per  cent.,  of  these  metallic  oxides,  it  is  called  boiled  oil; 
a  film  of  paint  made  with  this  oil  will  dry  in  twenty-four  hours, 
or  about  one -fifth  the  time  required  by  a  paint  made  with  raw 
oil.  Boiled  oil  is  commonly  made  by  the  larger  concerns  by 
heating  a  portion  of  oil  with  the  lead  and  manganese  oxides 
until  union  occurs;  this  is  then  added  to  the  larger  untreated 
portion  of  the  oil  and  thoroughly  mixed  with  it.  The  term 
drier  is  applied  to  the  lead  and  manganese;  it  is  also  used  in 
the  paint  business  to  mean  the  oil-soluble  compound  of  these, 
diluted  with  turpentine  or  other  solvent.  These  preparations 
are  of  many  kinds. 

Driers ;  How  Made. — The  most  simple  drier  is  made  by  heating 
a  gallon  of  oil  with  about  four  pounds  of  the  lead  and  manganese 


90  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

oxides— in  most  cases  there  is  a  large  amount  of  lead  and  a  small 
amount  of  manganese — at  a  high  temperature,  from  500°  to 
600°  F.,  until  combination  takes  place;  the  resulting  compound, 
which  is  black  in  color,  is,  while  still  warm,  dissolved  in  turpen- 
tine. This  high-temperature  drier  is  highly  oxidized.  A  much 
paler  drier  may  be  made  by  dissolving  the  lead  and  manganese 
in  a  larger  amount  of  oil  at  a  much  lower  temperature,  and 
finally  diluting  with  turpentine.  This  low-temperature  drier 
is  less  highly  oxidized,  and  driers  of  this  class  are  believed  to 
exert  a  less  injurious  action  on  paint  than  do  the  others,  though 
all  driers  lessen  the  durability  of  the  paint  in  some  degree.  Oil 
is  often  made  to  dry  rapidly  by  adding  some  of  these  made-up 
driers  to  the  oil,  cold;  such  oil  is  called  "bunghole  boiled  oil" 
and  is  not  commonly  thought  well  of;  but  some  of  the  best 
authorities  believe  that  such  oil,  if  made  with  a  low-temperature 
drier,  is  better  than  regular  boiled  oil;  and  it  is  a  significant 
fact  that  many  of  the  ready-mixed-paint  manufacturers  use  raw 
oil  and  prepared  driers,  which  they  would  not  do  if  they  thought 
it  bad  practice.  Such  driers  as  have  just  been  described  are 
pure  and  of  the  best  quality.  They  may  be  cheapened  by  using 
rosin  instead  of  oil,  or  by  using  rosin-oil  to  combine  with  the 
lead.  These  are  diluted  with  benzine  or  a  mixture  of  rosin 
or  rosin-oil  and  benzine,  and  the  odor  of  the  latter  disguised 
by  some  highly  odoriferous  essential  oil,  such  as  is  obtained  by 
the  distillation  of  wood.  Such  products  are  less  valuable,  but 
most  of  the  driers  on  the  market  are  made  in  this  way.  The 
common  compounds  used  for  making  driers  are  the  oxides,  but 
the  acetate  of  lead  and  the  borate  of  manganese  are  also  used. 
These  salts  are  white,  and  the  supposition  is  that  they  make 
pale  driers.  When  they  are  dissolved  by  heat  in  oil  the  acetic 
and  boric  acids  are.  driven  off,  as  the  salts  are  easily  decomposed 
and  the  acids  are  volatile,  and  there  is  probably  no  real  advantage 
in  their  use. 

Driers  Made  from  Soap. — Some  years  ago  there  was  a  great 
deal  of  drier  made  by  making  first  a  soda  soap  of  the  oil,  and 
decomposing  this  cold,  or  nearly  so,  with  an  aqueous  solution  of 


JAPANS  AND   DRIERS.  9 1 

the  metallic  salts,  using  the  acetate  or  nitrate  of  lead  and  the 
chloride  or  sulphate  of  manganese.  These  cold-formed  metallic 
soaps  were  then  dissolved  at  a  low  heat  in  suitable  solvents  which 
would  mix  with  oil.  Great  things  were  expected  of  these  driers, 
but  they  have  nearly  gone  out  of  use.  The  chemical  analysis  of 
a  drier  is  a  difficult  task,  and  when  the  results  are  obtained  they 
are  not  of  much  use.  To  obtain  special  effects  it  is  the  practice 
of  the  makers  to  mix  several  driers  of  different  qualities  in  certain 
proportions,  so  that  really  the  best  and  most  intelligent  use  of 
driers  is  an  art  rather  than  a  science  and  calls  for  the  knowledge 
of  a  specialist.  For  this  reason,  the  analysis  of  a  drier  is  of  com- 
paratively little  value.  To  secure  the  proper  drying  of  a  naturally 
slow-drying  paint  with  the  least  possible  amount  of  drier,  and  to 
get  the  drier  which  will  have  the  least  deleterious  effect  on  the 
paint,  is  a  problem  which  calls  not  only  for  a  great  deal  of  knowl- 
edge of  the  matter,  but  also  for  a  considerable  amount  of  experi- 
menting. A  factory  where  such  goods  are  made  ought  to  have  a 
laboratory  where  hundreds  of  carefully  conducted  and  recorded 
experiments  may  be  continually  carried  on.  And  when  we  come 
to  the  use  of  driers  in  varnish  and  varnish  paints,  the  intricacy 
and  difficulty  of  the  problems  become  greatly  increased,  and  even 
a  small  gain  is  often  of  great  value. 

Japans. — The  term  "  japan "  is  also  applied  to  substances 
which  promote  the  drying  of  a  paint-film.  It  cannot  be  said  that 
there  is  any  sharp  line  of  definition  between  what  are  called  driers 
and  what  are  called  japans,  but  what  we  usually  apply  the  latter 
term  to  is  a  liquid  which,  by  itself,  dries  to  a  hard  film  having 
considerable  coherence.  This  is  often  produced  by  the  use  of 
some  resin  in  the  compound,  not  common  rosin,  or  colophony,  but 
some  of  the  varnish-resins.  Such  a  compound  partakes  of  the 
nature  of  a  varnish,  and  some  of  the  japans,  such  as  those  in  which 
colors  are  ground  for  coach-painting,  are  practically  varnishes 
heavily  charged  with  lead  and  manganese.  Such  japans  would 
not  be  called  driers;  and  on  the  other  hand,  some  of  the  driers, 
notably  the  low-temperature  driers,  when  evaporated  leave  a 
greasy  metallic  soap  for  a  residue,  and  such  a  drier  would  not  be 


92  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

called  a  japan,  but  the  two  classes  shade  into  one  another,  and 
some  preparations  would  be  called  driers  by  one  man  and  japans 
by  another.  A  japan  always  has  a  drying  effect;  that  is,  when 
added  to  oil  it  promotes  oxidation  in  the  film.  The  term  "japan" 
is  also  applied  to  a  totally  different  class  of  preparations,  namely, 
such  varnishes  as  are  fused  on  the  surface  of  metals  and  other 
substances  by  subjecting  the  coated  article  to  the  heat  of  an  oven. 
These  are  also  called  baking-japans,  or  sometimes  baking-enamels, 
and  as  they  depend  on  the  action  of  heat  to  harden  them  they  are 
commonly  made  without  any  driers  in  them  at  all.  There  is  not 
the  least  resemblance  in  composition  or  use  between  these  japans 
and  the  other  kind. 

Bad  Effect  of  Driers. — The  danger  from  the  use  of  driers  in 
paint  is  this :  Where  oil  without  drier  dries  normally  it  absorbs  a 
certain  amount  of  oxygen  and  becomes  a  stable  substance;  no 
further  oxidation  takes  place;  but  if  it  contains  driers,  they  act 
as  carriers  of  oxygen,  and  although  their  action  is  enormously 
decreased  when  the  film  hardens,  it  does  not  absolutely  cease,  and 
the  effect  is  finally  to  oxidize  the  film  to  such  a  degree  that  its 
toughness  is  destroyed,  so  that  the  painter's  saying  that  the  drier 
burns  up  the  paint  is  absolutely  accurate.  Since  it  is  impracti- 
cable to  get  along  without  driers,  as  no  one  wishes  for  a  paint 
which  remains  wet  four  to  ten  days,  the  paint  expert  uses  all  his 
knowledge  and  ability  to  make  such  a  mixture  of  pigments  and 
such  a  combination  of  driers  as  shall  secure  the  greatest  immunity 
from  this  result,  in  many  cases  with  a  good  deal  of  success.  But 
the  "subject  is  so  intricate  that  it  is  impracticable  to  give  rules 
regarding  it. 

Low-temperature  Driers. — But  it  may  be  said  that  the  low- 
temperature  driers,  which  leave  a  greasy  film  when  spread  by 
themselves  on  glass  and  allowed  to  dry,  are  efficient  driers  in  oil 
when  added  in  small  proportions,  that  is,  up  to  the  point  where 
the  oil  itself  is  able  to  take  up  the  lead  and  manganese  contained, 
and  if  more  of  this  same  drier  is  added  the  excess  acts  as  though 
no  oil  were  present,  and  makes  the  film  softer  and  more  greasy, 
that  is  to  say,  slower  in  drying,  in  proportion  to  the  extra  amount 


JAPANS  AND   DRIERS.  93~ 

of  drier  added.  As  such  driers  are  made,  5  to  10  per  cent,  of  the 
liquid  drier  is  as  much  as  should  be  added  to  a  given  measure  of 
oil  or  oil-paint. 

Self-drying  Driers. — The  high-temperature  driers  and  japans, 
on  the  other  hand,  which  may  be  called  self-drying,  and  which 
when  spread  by  themselves  on  glass  dry  rapidly  to  a  hard  film, 
may  be  added  in  any  proportion  to  oil,  and  the  more  is  added  the 
more  rapidly  the  oil  will  dry ;  and  as  a  corollary,  oil  may  be  added 
to  dilute  and  slow  down  paints  ground  in  japan  or  a  self -dry  ing 
drier.  This  is  not  uncommonly  done,  in  carriage-painting  for 
instance,  where  the  paint  is  ground  to  a  paste  in  "grinding- japan.'* 

Grinding- japan. — A  grinding-japan  is  in  fact  a  varnish  so 
heavily  loaded  with  lead  and  manganese  that  it  dries  to  a  hard 
film  almost  immediately.  This  kind  of  japan  must  also  have 
the  property  of  mixing  with  the  pigments  used  by  the  carriage- 
painter  without  chemical  action,  so  that  the  paint  thus  made  may 
keep  without  decomposition  for  a  reasonable  length  of  time,  and- 
must  admit  of  being  thinned  either  with  oil,  or  turpentine,  or 
both.  From  the  fact  that  japans  are  mixed  frequently  with  oils 
it  is  not  very  uncommon  for  the  purchaser  to  think  that  the) 
should  mix  in  any  proportions  without  clouding,  that  is,  without 
the  precipitation  of  any  of  the  ingredients  of  the  japan.  This  is, 
however,  not  borne  out  by  practice,  for  the  japans  which  will  do 
this  usually  contain  little  or  no  lead,  which  is  the  ingredient  which 
should  enormously  preponderate  in  a  really  good  drier,  and  japans 
which  show  a  cloud  when  mixed  in  small  proportion  in  oil  are 
often  those  which  give  satisfaction  in  use. 

Curdling. — This  formation  of  a  dark  cloud  in  oil  is  spoken  of 
by  carriage-painters  as  "curdling"  the  oil,  but  no  curdy  precipi- 
tate is  formed.  The  real  value  of  a  grinding-japan  is  known 
only  by  its  practical  use.  It  is  easy  to  make  a  japan  that  will 
not  curdle,  but  none  such  has  come  under  the  observation  of  the 
writer  which  is  of  much  value  as  a  grinding-japan.  Another 
thing  which  often  unnecessarily  alarms  the  purchaser  is  the  de- 
position of  a  sediment,  or  "foots,"  from  a  clear  or  "bright"  japan 
or  drier.  This,  it  may  be  said,  is  almost  qr  quite  invariably  the. 


94  TECHNOLOGY  OF   PAINT  AND    VARNISH. 

case  with  driers  containing  lead  if  allowed  to  stand  a  consider- 
able time,  also  of  low-temperature  manganese  driers,  and  is  not 
to  be  taken  as  a  bad  sign  unless  it  goes  on  to  such  a  degree  that 
the  drying  effect  of  the  drier  is  evidently  impaired,  which  may 
sometimes  be  the  case  with  manganese  driers.  It  is  probably 
good  practice  to  avoid  carrying  a  very  large  stock  of  driers  and 
japans,  which  do  not  improve  by  age  beyond  two  or  three  months, 
and  in  general  it  may  be  said  of  varnishes  that  they  improve  with 
age  for  a  considerable  time,  and  then  do  not  deteriorate,  while 
paints  of  all  sorts,  and  especially  those  ground  in  varnish  and 
japan,  are  never  so  good  as  when  they  come  fresh  from  the  mill. 
It  is  obvious  that  as  the  chemical  composition  and  stability  of 
pigments,  and  especially  of  those  colors  called  "lakes,"  vary,  it  is 
desirable  to  use  with  them  such  japans  and  varnishes  as  will 
make  the  most  permanent  and  stable  mixtures;  this  is  only  to 
be  known  by  experiment,  though,  of  course,  the  experience  of  the 
manufacturer  is  a  valuable  guide  in  making  new  mixtures,  and  so 
it  comes  that  the  business  of  making  these  japan  colors  and  var- 
nish paints  is  largely  in  the  hands  of  the  varnish- makers,  who 
know  most  of  the  actual  composition  and  nature  of  the  materials 
used. 

The  activity  of  the  business  of  making  mineral  and  lake 
pigments,  which  is  incessant,  leads  to  the  continual  improvement 
(that  is,  change)  of  composition,  and  introduction  of  new  colors, 
and  there  is  likewise  change  in  varnish  materials,  especially  resins, 
and  processes;  so  that  a  considerable  proportion  of  the  formulae 
in  use  five  years  ago  are  now  out  of  date.  Even  where  names 
are  preserved  substances  change  and  formulae  become  mislead- 
ing. It  is  but  another  case  where  "the  letter  killeth;  the  spirit 
giveth  life." 


CHAPTER   IX. 
ROSIN. 

COMMON  rosin,  or  colophony,  is  the  residue  remaining  in 
a  still  after  the  spirit  of  turpentine  has  been  distilled  off  from 
the  crude  turpentine  which  is  obtained  from  the  pine-tree.  It 
is  commonly  supposed  that  this  crude  turpentine  consists  of 
colophony  dissolved  in  spirit  of  turpentine.  If  this  were  so, 
it  should  be  possible  by  redissolving  the  rosin  in  the  essential 
oil  to  reproduce  the  crude  turpentine,  but  this  is  not  possible; 
that  is,  it  is  easy  to  dissolve  the  rosin  in  the  spirit  of  turpentine, 
but  the  substance  so  obtained  does  not  much  resemble  crude 
turpentine. 

Spirit-  of  Turpentine  an  Artificial  Product.  —  The  charac- 
teristic and  peculiar  odor  of  spirit  of  turpentine  is  almost  or 
quite  absent  from  crude  turpentine,  and  the  probability  is  that 
the  latter  is  decomposed  by  the  heat  in  the  still,  and  that  the  spirit 
of  turpentine  and  colophony  are  both  products  of  this  decom- 
position, which  is  a  chemical  rather  than  a  physical  one,  being 
in  this  similar  to  the  change  which  we  know  takes  place  when 
ordinary  varnish-resins  are  melted  and  decomposed  in  the  varnish- 
kettle  by  heat.  In  the  latter  case  the  temperature  of  the  melting 
and  decomposing  resin  is  far  higher  than  that  of  the  vapor  given 
off,  thus  conclusively  proving  that  the  change  is  chemical  and 
that  the  liquid  which  distils  off  is  a  product  of  destructive  distil- 
lation, a  fact  which  we  know  from  other  reasons  also;  and 
although  the  writer  has  not  had  an  opportunity  of  running  a 
turpentine-still,  he  is  confident  that  a  destructive  distillation 
occurs  in  it  and  that  rosin,  or  colophony,  and  spirit  of  turpentine 
are  not  natural  substances,  but  products  of  chemical  action. 

95 


96  TECHNOLOGY  OF   PAINT  AND    VARNISH. 

Chemically  considered,  rosin  is  an  acid  substance;  it  in 
fact  consists  mainly  of  a  mixture  of  organic  acids  and  therefore 
it  has  a  strong  disposition  to  unite  and  combine  chemically 
with  basic  substances,  such  as  soda,  potash,  lime,  etc.  It  com- 
bines with  soda  and  potash  to  form  rosin  soap,  a  yellow  soap 
somewhat  similar  to  ordinary  tallow  soap.  This  will  mix  in 
all  proportions  with  common  soap,  and  as  it  is  not  entirely  with- 
out detergent  properties  and  is  very  cheap,  it  is  largely  used  as 
an  ingredient,  and  is  commonly  spoken  of  as  an  adulterant,  of 
laundry  soaps.  It  is  well  known  that  the  soda  and  potash  com- 
pounds are  soluble  in  water,  but  the  lime  soaps  are  not,  neither 
are  those  of  the  metals,  such  as  manganese  ,and  lead.  These 
lime  and  metallic  resinates  are  soluble  in  oil  or  turpentine  and 
are  used  in  varnish  and  driers.  The  resinates  of  lead  and  manga- 
nese being  efficient  and  cheap  driers  are  very  extensively  used. 
They  are  not  as  valuable  as  oil  driers,  their  influence  being 
more  deleterious  to  the  durability  of  whatever  they  are  put  in 
than  is  the  case  with  oil  driers,-  and  are  somewhat  unstable  com- 
pounds, which  makes  them  rather  unreliable.  Rosin  will  dissolve 
readily  in  oil,  and  a  varnish  may  be  made  in  this  way,  but  such 
a  varnish  remains  for  a  long  time  tacky  and  never  gets  very  hard, 
particularly  if  much  rosin  is  used. 

Rosin  Hardened  by  Lime.  —  It  has  been  found  that  the 
addition  of  from  2  to  10  per  cent,  of  lime  to  rosin  hardens  it  con- 
siderably, 5  or  6  per  cent,  of  lime  being  the  quantity  most  com- 
monly used;  it  is  added  to  the  melted  rosin  and  quickly  combines 
with  it,  but  a  part  settles  out,  it  having  been  found  more  con- 
venient and  expeditious  to  add  more  than  will  readily  combine 
under  the  common  conditions  of  heat  and  time  allowed.  This 
hardened  rosin  may  be  easily  dissolved  in  oil,  and  really  forms 
the  base  of  about  all  the  very  cheap  varnish  on  the  market.  A 
patent,  'which  has  now  expired,  for  this  lime-hardening  of  rosin 
was  granted,  but  the  process  was  before  that  well  known  to  all 
varnish- makers  and,  so  far  as  is  known  to  the  author,  no  regard 
was  ever  paid  to  the  patent,  in  this  country  at  least.  I  am 
told  that  it  is  described  in  an  English  book  of  the  eighteenth 


ROSIN.  97 

century.  As  a  general  rule,  when  rosin  is  spoken  of  by  American 
varnish- makers  they  refer  to  this  lime-hardened  article,  which 
they  prepare  as  they  want  it.  The  common  practice  is  to  use 
pulverized  quicklime;  formerly  slacked  lime,  or  calcic  hydrate, 
or  a  mixture  of  that  and  carbonate  was  used.  Varnish  may  also 
be  made  by  dissolving  rosin,  either  in  its  natural  state  or 
hardened,  in  turpentine  or  benzine,  making  a  product  some- 
what like  damar  varnish,  and  this  is  used  to  adulterate  damar 
varnish  or  as  a  substitute  for  it;  it  is  also  used  to  adulterate 
other  varnishes.  One  of  the  most  important  uses  of  rosin  var- 
nish is  as  an  adulterant  of  regular  oleo-resinous  varnishes,  but  a 
large  amount  is  sold  for  use  without  any  admixture  of  the  more 
valuable  ingredients.  These  rosin  varnishes  are  pale  in  color 
as  a  rule,  and  of  a  brilliant  lustre  when  recently  applied.  They 
are  free  or  nearly  so  from  most  of  the  "tricks"  (formation  of 
an  uneven  and  imperfect  surface)  to  which  better  varnishes 
are  liable,  but  they  qjjp  not  usually  dry  to  a  very  hard  surface 
(but  much  progress  has  been  made  in  late  years  in  this  regard), 
and  they  lack  durability,  especially  when  exposed  to  the  weather. 

Good  Effect  in  Mixtures.  —  The  addition  of  a  very  small 
proportion  of  rosin  varnish  to  an  oleo-resinous  varnish  often 
makes  it  ready  for  use  in  a  short  time.  This  may  be  due  to 
two  causes,  one  of  which  is  that  the  rosin  is  acid  and  combines 
with  any  of  the  excessively  minute  particles  of  lead  or  manga- 
nese which  may  be  floating  in  the  varnish  and  which  would 
cause  flaws  and  imperfections  in  its  surface;  the  other  that  rosin 
is  slow  to  set  and  harden  and  may  act  in  the  film  as  a  flux,  causing 
the  film  to  flow  more  evenly  and  thus  making  a  more  perfect 
surface. 

It  may  not  be  necessary  to  add,  in  order  to  secure  these  results, 
more  than  3  to  5  per  cent,  of  rosin  varnish  containing  a  still  smaller 
per  cent,  of  actual  rosin,  and  this  small  amount  may  not  be  enough 
to  be  sensibly  deleterious,  especially  in  a  varnish  of  moderate 
price  and  ordinary  character.  As  a  general  rule,  the  addition 
of  rosin  varnish  is  made  in  considerable  quantity,  as  it  must  be 
to  sensibly  affect  the  price,  and  is  an  injurious  ingredient. 


98  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

Viscosity  of  Rosin. — Rosin  is  a  brittle  solid,  easily  reduced 
to  a  powder,  but  if  we  lay  a  piece  of  rosin  on  a  board,  even  in  a 
moderately  cool  room,  it  will  in  time  flow  out  into  a  flat  cake.  If 
we  remove  the  head  from  a  barrel  of  rosin  and  lay  the  barrel 
on  its  side,  the  rosin  will  in  time  flow  out.  It  is  in  fact  inter- 
mediate in  its  properties  between  a  solid  and  a  liquid,  being 
extremely  viscous.  It  is  very  easily  melted,  and  as  a  liquid  has 
unusual  solvent  qualities;  it  is  a  very  effective  flux. 

This  was  known  to  the  old  varnish- makers,  who,  as  has  been 
seen  in  the  recipes  already  given,  often  put  a  small  proportion 
of  it  in  the  kettle  in  which  they  were  about  to  melt  their  resin; 
by  doing  so,  the  regular  varnish  resin  was  much  more  easily 
melted.  Sometimes  a  little  oil  was  added  for  the  same  purpose. 
It  was  common  to  rub  the  inside  of  the  kettle  with  oil  before 
putting  it  on  the  fire,  but  rosin  is  much  more  effective. 

Used  with  Asphaltum. — Rosin  easily  dissolves  and  is  dis- 
solved by  the  asphaltums  when  melted,  and  is  a  common  ingre- 
dient of  asphaltum  varnishes  and  compounds.  It  adds  so 
greatly  to  the  working  qualities  of  these  asphaltum  compounds 
that  it  is  difficult  to  resist  the  temptation  to  put  it  in,  and  since 
most  of  the  asphaltum  compounds  and  varnishes  are  sold  at  a 
low  price,  and  as  rosin  is  the  very  cheapest  thing  used  in  the 
business,  the  temptation  is  twofold. 

Rosin  Varnish  Cracks. — Every  one  must  have  observed  on  old 
doors  and  sometimes  on  old  furniture,  especially  chairs,  that  the 
paint  is  cracked  and  the  cracks  have  opened  to  a  considerable 
width,  frequently  a  quarter  of  an  inch,  in  a  reticulated  pattern 
suggestive  of  alligator-leather.  These  cracks  are  at  first  minute; 
then  the  paint  or  varnish  on  the  interspaces  contracts,  drawing 
slowly  apart,  until  the  cracks  become  wide  bare  strips.  In  nearly 
all  cases  this  is  due  to  the  use  of  rosin  varnish,  either  by  itself  or 
as  a  considerable  ingredient  in  a  paint.  India-rubber  as  a  con- 
stituent of  paint  or  varnish  will  act  in  the  same  way;  but  prac- 
tically it  is  not  in  use.  If  a  rosin  varnish  is  made  with  very  little 
oil,  it  presents  at  first  a  brilliant  and  glassy  surface,  because  of  the 
high  percentage  of  resinous  material,  but  the  air  rapidly  acts  on 


ROSIN.  99 

it,  possibly  because  the  minute  proportion  of  ammonia  in  the  air 
(which  is  much  higher  indoors  than  without)  chemically  attacks 
the  rosin,  but  also  because  pure  air  acts  on  it  as  well,  and  in  a  short 
time  the  lustre  is  greatly  reduced;  then  it  begins  to  show  under  a 
magnifying-glass  minute  cracks;  these  grow  larger;  after  a  time 
the  whole  of  the  varnish  cracks  in  pieces  and  comes  off.  If  a 
considerable  amount  of  oil  is  used,  the  lustre  is  not  at  first  as 
good,  and  although  it  nearly  disappears  in  a  comparatively  short 
time,  the  varnish  lasts  much  longer  than  the  one  just  described, 
and  it  is  this  sort  of  varnish  (or  the  first  kind  mixed  with  an  oil- 
paint,  which  has  the  same  effect  in  increasing  the  proportion  of 
oil)  which  shows  the  wide  reticulated  cracks  spoken  of;  the 
rosin  varnish  which  is  nearly  all  rosin  usually  falls  off  entirely 
before  the  cracks  become  so  wide. 

Rosin  may  be  hardened  by  zinc  oxide,  or  by  white  lead,  instead 
of  lime,  and  a  rosin  "ester"  has  been  made  in  which  the  rosin 
acids  are  combined  with  glycerine ;  these  products  are  better  than 
the  lime-hardened  article,  but  they  also  cost  more  and  are  darker 
in  color,  and  it  soon  becomes  apparent  that  a  varnish  can  be  made 
for  about  the  same  money  out  of  a  cheap  Manila  or  other  cheap 
resin,  which  will  be  for  actual  use  worth  ten  or  twenty  times  as 
much  as  the  rosin  varnish;  so  that  practically  the  limed  rosin  is 
the  compound  in  actual  use.  Most  of  the  recent  writers  on  the 
subject  have  laid  stress  on  the  fact  that  lead  and  manganese  tend 
to  shorten  the  life  of  paint  and  varnish;  the  writer  of  this  has 
been  as  strenuous  in  insisting  on  this  as  anybody;  but  the  fact  is 
that,  excepting  a  small  amount  of  varnish  for  special  and  very 
limited  use,  all  varnishes  except  rosin  contain  some  lead;  the 
manganese  is  commonly  so  small  in  amount  as  to  escape  detection 
by  chemical  analysis,  though  not  unimportant  in  its  action ;  but 
the  presence  of  lead  in  a  varnish,  being  with  our  present  practice 
unavoidable,  is  not  to  be  taken  as  an  objection,  but  rather  the 
contrary,  while  varnish  containing  lime  may'  be  confidently  re- 
jected, as  being  a  rosin  varnish.  The  author  does  not,  however, 
regard  the  absence  of  lime  as  a  definite  proof  of  absence  of  rosin, 
for  evidence  is  at  hand  that  rosin  varnishes  are  made  without 


100  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

lime,  although  the  writer  does  not  know  as  yet  how  they  are 
made;  the  making  of  rosin  varnishes  is  quite  an  industry  by 
itself,  and  those  who  are  engaged  in  it  undoubtedly  have  been 
working  out  processes  and  using  materials  not  known  to  those 
who  are  less  familiar  with  that  branch  of  the  business.  It  is  not 
to  be  supposed  that  rosin  varnishes  as  a  rule  do  not  contain  some 
lead  and  manganese ;  as  a  rule  they  do.  Rosin  is  so  soft  that  var- 
nishes containing  it  naturally  dry  slowly,  and  the  makers  put  in 
anything  which  will  hasten  their  drying;  but  it  is  possible,  and  not 
very  uncommon,  to  make  rosin  varnish  without  these  driers. 

I  cannot  refrain  from  giving  an  illustration.  Some  years  ago 
I  had  occasion  to  give  advice  about  varnishing  the  woodwork — 
posts,  beams,  doors,  etc. — of  a  chemical  laboratory  in  one  of  our 
universities.  As  I  have  spent  the  greater  part  of  my  life  in  a 
laboratory  and  not  a  little  of  it  in  the  varnish  business,  it  did  not 
occur  to  me  that  I  did  not  know  practically  how  to  varnish  a 
laboratory,  and  I  advised  using  a  varnish  with  about  20  gallons 
of  oil,  and  made,  as  nearly  as  I  now  recollect,  of  Kauri,  Benguela, 
and  Zanzibar  resins.  The  head  professor  of  chemistry  had,  how- 
ever, formed  the  idea  that  lead,  even  in  traces,  was  objectionable, 
not,  however,  because  of  its  oxidizing  action,  but  because  he 
feared  it  would  be  attacked  by  sulphuretted  hydrogen,  which  is 
always  present  in  the  air  in  such  a  laboratory.  Of  course  all 
chemists  know  that  it  does  attack  lead,  and  white-lead  paint  in 
a  laboratory  quickly  becomes  blackened  from  the  conversion  of 
the  carbonate  into  sulphide ;  but  in  varnish  there  is  very  little  lead, 
and  what  there  is  is  probably  so  firmly  combined  that  hydrogen 
sulphide  cannot  attack  it ;  and  besides  all  that  the  fact  is  that  any 
decent  varnish  is  nearly  impermeable  to  gases  after  it  has  become 
well  hardened ;  it  wastes  away  from  the  outer  surface,  or  it  cracks 
from  too  rapid  changes  of  temperature,  or  it  is  thrown  off  by 
moisture  in  the  underlying  wood,  trying  in  vain  to  pass  through 
it,  but  it  is  not  penetrated  and  decomposed  throughout  by  gases, 
so  that  the  reasoning  which  applies  to  an  oil  and  pigment  paint 
does  not  bear  on  the  varnish  problem;  but  this  was  all  unknown 
to  the  professor  of  chemistry,  a  man  of  much  learning  and  eminent 


ROSIN.  I0i 

in  his  own  way,  and  he  insisted  on  having  a  varnish  free  from 
lead.  I  gave  it  up,  wondering  in  my  own  mind  what  new  and 
unknown  star  was  arising  in  the  varnish  world  who  had  solved  the 
problem  of  making  a  raw-oil  varnish  without  driers  for  such  use. 

The  next  time  I  saw  the  laboratory  I  found  out.  That  beau- 
tiful building  had  been  subjected  to  the  outrage  of  varnishing  it 
with  the  meanest  kind  of  a  rosin  varnish,  a  cheap  and  much  worse 
than  worthless  "hard  oil  finish,"  three-fourths  of  which  had 
decomposed  and  fallen  off,  leaving  dingy  patches  of  rosin  on  the 
blackened  surface  of  the  wood.  But  it  had  no  lead  in  it,  nothing 
but  lime.  In  the  same  building  the  desks,  stair-railings,  etc.,, 
which  had  been  bought  ready-made  from  some  respectable  man- 
ufacturers, and  varnished  with  a  good  though  not  expensive  var- 
nish, were  in  as  good'  condition  as  when  bought,  ordinary  wear 
excepted. 

Rosin  Size. — A  solution  of  rosin,  without  any  treatment,  in 
benzine  is  probably  the  cheapest  varnish  in  use.  I  have  seen  it 
sold  in  barrels  for  nine  cents  per  gallon,  f.o.b.  cars.  It  is  used 
for  varnishing  building-paper  and  the  like,  but  building-paper  is 
sometimes  sized  with  a  rosin  size,  which  is  added  to  the  pulp, 
and  a  great  deal  of  this  size  is  used  for  varnishing  wall-paper. 

The  rosin  varnishes  are  much  less  impermeable  to  water  than 
those  made  from  standard  varnish-resins,  and  when  a  rosin  var- 
nished surface  is  wet  with  water  it  usually  turns  whito  because 
of  the  action  of  the  water  on  the  rosin.  Many  varnishes  not  con- 
taining rosin  do  this  also,  but  not  so  readily,  nor  does  the  water 
penetrate  them  so  deeply. 

Sponge  Test. — If  we  place  on  a  flat  horizontal  varnished  sur- 
face a  wet  sponge,  and  leave  it  overnight,  we  shall  find  in  the 
morning  whether  the  water  has  acted  on  it  or  not.  A  rosin 
varnish  will  be  white  under  the  sponge,  and  frequently  it  will 
be  dissolved  out  down  to  the  wood  or  nearly  so,  and  this  white 
surface  will  remain  white  when  dry,  showing  deep  corrosion.  A 
better  varnish,  although  it  may  turn  white,  will  regain  its  original 
color  on  drying,  and  a  varnish  made  expressly  to  stand  water 
ought  not  to  be  affected. 


102  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

Rubbing  Test. — If  the  reader  will  rub  the  varnished  surface 
of  a  piano  or  of  any  good  piece  of  varnished  furniture  with  the 
ball  of  the  finger,  he  will  find  that  no  effect  is  produced,  except 
to  increase  the  polish;  but  if  the  same  thing  is  done  to  a  surface 
covered  with  rosin  varnish,  the  latter  can  be  rubbed  off  in  this 
way,  showing  that  it  is  softer  and  less  tough  than  the  better 
article. 

Rosin  varnishes  are  chiefly  used  on  the  woodwork  of  the 
cheaper  class  of  houses,  on  cheap  furniture,  and  on  agricultural 
machinery.  They  are  also  used  to  mix  with  the  better  varnishes 
in  order  to  reduce  the  price,  and  there  is  a  great  retail-store  trade 
in  these  goods.  Every  retail  dealer  in  paint  .and  varnish  keeps 
two  or  three  barrels  of  rosin  varnish  on  tap,  from  which  he  sells 
varnish  to  the  house-painters  and  other  people  under  any  name 
by  which  they  may  demand  it.  It  is  probable  that  more  rosin 
varnish  is  sold  than  of  all  the  rest  put  together.  It  cannot  be 
denied  that  progress  is  being  made  in  producing  better  qualities 
of  these  goods,  but  it  does  not  now  seem  likely  that  they  will  ever 
equal  the  varnishes  made  from  the  natural  resins,  either  in 
appearance  or  durability. 


CHAPTER  X. 

SPIRIT  VARNISHES. 

IF  we  put  some  shellac  resin,  or  gum  shellac  as  it  is  called, 
in  a  bottle  with  somewhat  more  alcohol  than  enough  to  cover  it, 
and  let  it  stand  a  day  or  two,  occasionally  shaking  it,  the  greater 
part  of  the  resin  will  dissolve,  making  shellac  varnish.  The 
solution  will  take  place  much  more  promptly  if  the  bottle  is 
placed  in  a  shaking- machine,  or  attached  to  a  revolving  shaft, 
and  the  common  way  of  making  shellac  varnish  is  to  put  the 
components  in  a  revolving  barrel  or  churn,  or  in  a  mixer  where 
the  materials  are  agitated  by  a  stirrer.  In  any  case,  it  is  done 
without  the  application  of  heat,  and  the  varnish  thus  made  is 
a  spirit  varnish  containing  no  oil,  nothing  but  a  resin  and  a 
volatile  solvent.  The  part  which  does  not  dissolve  is  a  sort  of 
wax,  in  appearance  (when  purified)  not  unlike  carnauba  wax; 
this  is  soluble  in  benzine,  and  may  be  removed  from  the  shellac 
proper  by  the  use  of  that  solvent,  leaving  a  clear  and  transparent 
solution  of  the  pure  resin  in  alcohol. 

When  shellac  varnish  is  spread  on  a  surface  the  alcohol 
evaporates  and  the  resin,  or  the  mixture  of  resin  and  wax,  is 
left  as  a  film  of  exactly  the  same  composition  as  the  original 
resin;  the  office  of  the  alcohol  having  been  to  facilitate  the 
mechanical  operation  of  spreading  the  resin  out  in  a  thin  film  of 
nearly  uniform  thickness.  This  is  very  different  from  the  action 
of  oil  in  oleo-resinous  varnishes,  which  not  only  helps  to  reduce 
the  resin  to  a  liquid  condition,  but  itself  remains  as  an  important 
and  valuable  part  of  the  film.  Shellac  varnish  is,  therefore, 
essentially  different  from  those  varnishes  which  have  so  far  been 

103 


104  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

described.     It  is  the  most  generally  used  and  the  most  important 
of  the  spirit  varnishes. 

Composition  of  Shellac  Varnish. — The  English  and  European 
books  on  this  subject  commonly  contain  formulae  for  making 
it  with  from  five  to  fifteen  or  twenty  parts  by  weight  of  alcohol 
to  one  part  of  shellac.  This  will  make  a  very  thin  varnish  and 
is  not  known  commercially  in  this  country,  where  ordinary  or 
standard  shellac  varnish  is  made  with  five  pounds  of  gum  shellac 
to  one  gallon  of  95  or  97  per  cent,  alcohol,  or  about  one  part  by 
weight  of  shellac  to  one  and  one-half  parts  by  weight  of  alcohol. 
This  makes  a  varnish  of  rather  heavy  body,  but  one  which  may 
be  brushed  out  thin,  and  will  dry  quickly.  All  varnishes  should 
be  put  on  in  thin  coats,  but  shellac  is  remarkable  in  this  respect, 
for  if  put  on  thin  it  dries  very  quickly  and  if  put  on  thick  it  takes 
on  a  waxy  consistency  and  is  excessively  slow  about  getting  hard. 

Precautions  in  Using  Shellac. — One  or  two  thin  coats  of 
shellac  may  be  applied  and  the  object  put  to  almost  immediate 
use,  but  great  care  should  be  observed  in  using  more  than  two 
coats  or  this  persistently  tacky  condition  may  be  encountered. 
As  shellac  is  a  varnish  very  commonly  used  by  amateurs,  this  is 
worth  remembering.  Shellac  very  easily  softens  and  melts  with 
heat,  and  if  it  is  used  as  a  first  coat  on  woodwork  and  an  oleo- 
resinous  varnish  put  over  it,  the  object  so  coated  should  not  be 
placed  near  a  fire  or  in  the  hot  sun,  lest  the  shellac  soften  and 
blisters  be  formed. 

The  natural  color  of  shellac  is  brownish  yellow  or  reddish 
yellow,  and  it  is  commonly  spoken  of  as  orange.  The  different 
grades  are  designated  by  letters,  D.  C.  being  the  best  (the  letters 
are  the  initials  of  David  Campbell).  It  is  reported,  and  is  prob- 
ably true,  that  large  quantities  of  common  rosin  are  shipped  to 
India  and  used  as  an  adulterant  of  gum  shellac  in  making  the 
cheap  grades. 

Shellac  is  easily  bleached  with  chlorine,  becoming  nearly 
white,  and  called  then  white  shellac. 

Orange  shellac  is  soluble  in  85  per  cent,  alcohol,  but  white 
shellac  which  is  bleached  in  an  alkaline  aqueous  solution,  from 


SPIRIT   VARNISHES.  105 

which  it  is  recovered  by  acidifying  the  solution,  contains  some 
water  and,  perhaps  for  this  reason,  requires  strong  alcohol,  95 
to  97  per  cent.,  to  dissolye  it.  Some  of  this  water  may  be  re- 
moved by  coarsely  powdering  the  shellac  and  exposing  it  on 
trays  to  dry  air  in  a  warm  but  not  too  hot  room. 

Insoluble  White  Shellac. — If  too  much  heat  be  applied,  or 
if  the  drying  operation  be  too  prolonged,  the  white  shellac  is 
very  liable  to  go  over  into  an  isomeric  state  and  is  then  perfectly 
insoluble.  It  is,  therefore,  stored  in  a  cool  damp  place  and 
when  wanted  is  got  into  solution  with  the  utmost  expedition. 
Orange  shellac  requires  no  such  care  and  may  be  used  even 
after  it  has  been  melted. 

Shellac  is  not  only  soluble  in  common  grain-alcohol  (ethyl 
alcohol),  but  also  in  wood- alcohol  (methyl  alcohol),  and  in  some 
of  the  other  alcohols,  but  ethyl  and  methyl  alcohols  are  the  ones 
commonly  used.  It  is  readily  soluble  in  ammonia-water,  also 
in  aqueous  solutions  of  borax  and  of  the  carbonates  of  soda  and 
potash. 

Alkaline  Solutions. — The  ammonia  solution  has  had  some 
use,  especially  as  a  polish  for  shoes,  etc.,  and  the  borax  solution 
has  some  commercial  use,  especially,  I  have  heard,  as  a  glaze 
for  straw  hats.  Any  of  these  varnishes  may  be  colored  by  the 
addition  of  a  suitable  dye  or  may  be  made  into  a  varnish  paint 
with  a  pigment  which  has  no  chemical  action  on  the  shellac. 
There  are  places  where  shellac  is  the  best  varnish  that  can  be 
used;  for  instance,  nothing  equals  it  for  varnishing  the  wooden 
patterns  from  which  castings  are  to  be  made,  and  for  floors  on 
ships  where  it  is  absolutely  necessary  that  they  should  be  ready 
for  use  within  an  hour  or  two  after  they  are  varnished;  it  is, 
in  fact,  used  not  a  little  for  a  floor  varnish  in  houses,  but  it  lacks 
durability,  and  in  general  it  is  easily  destroyed  if  exposed  to  the 
weather.  It  dries  more  quickly  than  any  other  common  varnish 
and  on  that  account  is  very  useful. 

Damar  Varnish. — As  shellac  may  be  taken  as  a  type  of  the 
alcoholic  varnishes,  so  damar  may  represent  that  class  which  has 
an  essential  oil  as  the  solvent.  Damar  varnish  is  made  by  dis- 


106  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

solving  damar  resin  in  spirit  of  turpentine.  This  may  be  done 
cold,  in  a  revolving  barrel  or  churn,  or  hot  in  a  kettle.  If  the 
latter,  it  is  common  to  dissolve  it  in  a  small  amount  of  turpentine, 
and  when  it  is  dissolved  thin  with  the  necessary  amount  of  cold 
turpentine.  This  lessens  the  fire  risk.  It  is  not  a  perfect  solu- 
tion, remaining  persistently  cloudy,  an  opaque  white  liquid, 
becoming  more  translucent  by  standing  a  long  time.  It  dries  by 
the  evaporation  of  the  solvent,  but,  as  has  been  said  before,  tur- 
pentine does  not  wholly  evaporate,  part  of  it  becoming  oxidized 
and  remaining  as  an  elastic  resinous  ingredient  of  the  film.  Damar 
itself  is  not  a  hard  resin,  but  it  is  very  white  and  the  varnish  film 
never  becomes  very  hard  (unless  by  baking),  nor  is  it  very  dura- 
ble, even  within  doors,  but  its  extreme  paleness  and  the  ease  with 
which  it  may  be  used  cause  it  to  be  very  popular.  f°  cheapen  it, 
benzine  is  often  mixed  with  the  turpentine  and  rosin  with  the 
damar  resin ;  in  fact,  not  a  little  is  sold  under  the  name  of  damar, 
which  contains  no  damar  and  no  turpentine.  Mixtures  of  this 
sort  may  be  made  which  will  deceive  all  but  the  very  elect.  Per- 
haps some  of  these  are  about  as  good  as  the  straight  damar,  which 
is  not  a  very  good  varnish  anyway;  still,  the  people  who  use  it  for 
fine  work,  such  as  fine  baking  enamels  in  delicate  colors,  can  tell 
the  difference  and  not  only  insist  on  pure  damar,  but  like  that 
made  from  selected  pieces  of  resin.  There  is  a  general  belief 
that  if  it  is  made  by  the  cold  process  it  is  better  than  if  made 
hot.  It  is  usually  made  by  dissolving  five  or  six  pounds  of 
damar  resin  in  one  gallon  (seven  and  one-fifth  pounds)  of  spirit  of 
turpentine.  It  should  be  allowed  to  settle  for  sixty  days  before 
using. 

Sandarac. — Another  resin  of  some  importance  is  sandarac. 
As  has  been  already  frequently  stated,  this  was  one  of  the  first 
known  of  the  resins,  and  varnishes  were  made  of  it  perhaps  in 
prehistoric  times;  certainly  in  early  times.  It  is  soluble  in  alco- 
hol (not  perfectly),  also  not  very  perfectly  in  spirit  of  turpentine, 
with  heat  in  oil,  and  has  been  a  considerable  and  frequently  the 
most  important  ingredient  in  varnishes  of  a  complex  character. 
It  may  be  observed — and  the  observation  really  lies  at  the  foun- 


SPIRIT   VARNISHES.  107 

dation  of  the  art  of  making  spirit  varnishes — that  when  a  resin  is 
found  to  be  only  partially  soluble  in  a  liquid,  complete  solution 
may  be  attained  by  adding  some  other  resin  to  the  mixture; 
sometimes  by  adding  the  dry  resin,  at  others  by  dissolving  the 
second  resin  in  the  same  or  some  other  solvent  and  mixing  the 
solutions.  Common  rosin,  or  colophony,  is  remarkably  efficient 
in  this  respect,  and  it  is  said  that  Venice  turpentine,  Burgundy 
pitch,  and  the  like  are  also  valuable.  Sometimes  a  resinous 
solution  will  dry  flat,  i.e.,  white  and  opaque,  and  the  addition  of 
a  portion  of  some  other  varnish  will  cure  this  tendency,  making 
the  film  full  and  transparent.  Thus  the  art  of  making  spirit 
varnishes  is  one  of  great  complexity,  and  the  writer  of  this  is  no 
more  than  an  amateur  in  this  kind  of  work.  His  advice  and 
information  to  the  reader  will,  therefore,  be  correspondingly 
scanty. 

Sandarac,  when  new  and  fresh,  is  of  a  pale-yellow  color,  and 
with  age  becomes  reddish  and  darker;  when  applied  as  a  varnish 
it  is  left  on  the  surface  as  a  resin  and,  as  would  naturally  be  sup- 
posed, darkens  and  becomes  red.  This  has  long  been  known,  for 
it  has  been  used  from  early  times  to  varnish  pictures,  and  its 
effect  on  their  colors  was  a  subject  of  comment  among  the  painters 
of  the  middle  ages.  They  usually  dissolved  it  in  turpentine  and 
commonly  added  some  other  resin  to  the  solution. 

What  has  been  said  about  sandarac  may  be  applied  to  mastic : 
it  is  only  partially  soluble  in  the  ordinary  solvents;  alcohol  dis- 
solves about  nine-tenths  of  it;  turpentine  is  also  a  common  sol- 
vent for  it.  It  is  paler  than  sandarac  and  does  not  redden  or 
darken  with  age.  It  is  somewhat  softer  than  sandarac. 

Damar,  shellac,  sandarac,  mastic,  and  common  rosin  are 
(except  asphaltum,  to  be  spoken  of  later)  the  only  resins  com- 
monly sold  by  dealers  in  varnish  resins  in  this  country  for  mak- 
ing varnishes  of  this  class,  i.e.,  solutions  of  resin  in  volatile  sol- 
vents, without  oil.  There  are  many  other  resins  soluble,  or  partly 
so,  in  alcohol  or  turpentine,  which  are  said  to  be  and  probably  are 
used  in  spirit  varnishes,  prominent  among  which  are  elemi,  Venice 
turpentine,  Burgundy  pitch,  and  benzoin;  these  are  to  be  had 


108      .          TECHNOLOGY  OF  PAINT  AND    VARNISH. 

from  importers  and  dealers  in  drugs  and  are  by  them  said  to  be 
used  in  the  manufacture  of  medicinal  preparations,  plasters,  and 
the  like,  and  toilet  articles.  Probably  a  small  amount  also  goes 
to  the  spirit-varnish  makers,  but  the  market  shows  that  the  resins 
first  mentioned  are  the  ones  from  which  nearly  all  the  spirit 
varnishes  are  made.  There  are  also  a  number  of  tinctorial  resins, 
such  as  turmeric,  gamboge,  dragon's  blood,  annatto,  and  the  like, 
but  the  spirit -soluble  coal-tar  colors  have  largely  displaced  them, 
so  that  they  are  hardly  worth  mention.  The  opinion  of  the 
writer,  founded  on  considerable  evidence  and  some  knowledge  of 
the  subject,  but  yet  not  that  of  an  expert,  is  that  shellac  cleared 
of  wax  is  the  foundation  for  most  of  the  spirit  'varnish,  its  defects 
corrected  by  mastic  and  sandarac  (which  latter  are  also  used  con- 
siderably without  shellac),  and  cheapened  when  necessary  with 
rosin.  The  solvent  is  chiefly  wood-  or  grain-alcohol,  more  fre- 
quently the  former,  not  only  because  it  is  cheaper  but  because  it 
is  better  for  making  the  wax-free  shellac  solution. 

Alcohol  will  dissolve  about  20  per  cent,  of  benzine,  and  this  may 
sometimes  be  used  to  cheapen  the  mixture,  and  probably  in  some 
cases  to  increase  its  solvent  power,  and  a  little  oleo-resinous  var- 
nish or  a  little  oil  may  be  added  in  some  instances  to  give  certain 
qualities.  There  are,  of  course,  other  solvents,  the  most  im- 
portant being  coal-tar  naphtha,  great  quantities  of  which  are  used 
in  making  varnish  for  ships'-bottom  paints;  amyl  acetate  and 
fusel-oil,  which  are  used  in  the  pyroxylin  varnishes,  and  carbon 
disulphide,  used  in  certain  asphaltum  paints;  and  solvents  ob- 
tained in  the  fractional  distillation  of  wood-tar  are  used  in  var- 
nishes which  are  made  and  used  in  certain  manufacturing  opera- 
tions, but  the  spirit  varnishes  of  the  market  are  probably  of  the 
composition  indicated.  A  considerable  quantity  is  imported, 
chiefly  from  France,  and  it  is  commonly  believed  in  this  country 
that  the  French  make  more  spirit  varnishes,  and  know  more  of 
them,  than  do  the  people  of  any  other  country,  although  they  are 
believed  to  be  deficient  in  knowledge  of  the  better  sorts  of  the 
oleo-resinous  varnishes. 

Closely  allied  to  the  spirit  varnishes  are  some  of  those  made 


SPIRIT   VARNISHES.  109 

with  asphaltum.  This  is  a  black  or  brownish-black  resinous 
mineral,  soluble  in  spirit  of  turpentine,  and  when  melted  mixing 
in  all  proportions  with  linseed-oil,  also  with  melted  rosin,  and  the 
solutions  of  it  mix  readily  with  the  oleo-resinous  varnishes.  Like 
rosin,  it  has  considerable  effect  as  a  flux;  but  unlike  rosin,  the  hard 
varieties  are  highly  permanent  and  durable,  and  where  the  color 
is  not  an  objection,  it-  is  a  valuable  ingredient  in  oleo-resinous 
varnishes.  It  has  a  rather  bad  name,  due  to  several  causes.  In 
the  first  place,  its  warm  brownish-black  translucent  color  (in  a 
thin  film)  has  always  been  an  attraction  to  artists,  and  the  artist 
is  too  often  totally  and  phenomenally  ignorant  of  the  materials, 
and  especially  of  the  vehicles  and  varnishes,  which  he  uses,  but 
not  lacking  in  confidence.  Hence  asphaltum  dissolved  in  turpen- 
tine has  been  used,  and  this,  especially  if  -mixed  with  rosin,  is 
merely  a  spirit  varnish,  and  is  one  of  the  most  perishable  of  var- 
nishes, because  the  vehicle  evaporates  and  leaves  the  asphalt  in 
a  thin  film,  which  either  immediately  or  very  soon  becomes  a 
powder;  or,  if  mixed  with  rosin,  cracks;  and  in  any  case  is  almost 
certain  to  partly  dissolve  or  be  dissolved  in  the  other  paints  used 
on  the  same  work,  dissolving  and  destroying  them.  For  these 
and  other  reasons  the  belief  has  grown  up  among  artist  painters 
that  asphaltum  is  unstable  and  in  every  way  dangerous.  This  is 
all  wrong. 

Stability  of  Asphaltum. — The  great  painters  of  the  middle 
ages  used  asphaltum  freely,  and  in  their  hands  it  proved  abso- 
lutely permanent,  and  Eastlake  says  that  there  are  no  complaints 
by  any  of  the  writers  of  that  period  of  its  flowing  or  cracking. 
The  reason  is  that  they  used  it  in  a  true  oleo-resinous  varnish, 
which  dries  too  slowly  for  modern  practice,  but  which  is  the  only 
way  to  attain  permanence.  Another  reason  for  its  evil  repute  is 
that  it  has  been  and  is  largely  used  as  a  cheap  black  varnish  for 
small  (and  large)  pieces  of  iron  used  in  the  arts  and  manufac- 
tures, as  an  inexpensive  temporary  finish,  keeping  them  from 
rusting  until  they  come  into  the  hands  of  the  consumer.  The 
way  to  make  a  cheap  asphaltum  varnish  is  to  melt  it  with  rosin 
and  thin  with  benzine.  The  most  durable  asphaltum  is  not  very 


no  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

black,  but  brown  and  translucent  as  a  film,  so  a  softer  and  blacker 
material  is  used,  much  more  opaque  but  less  durable.  This  is 
not  all.  Much  cheaper  than  asphaltum  is  coal-tar  pitch,  and  a 
great  deal  of  asphaltum  varnish  is  made  of  this,  which  is  inferior 
to  asphaltum  in  every  respect,  even,  unfortunately,  in  price.  Such 
varnishes  are  sold  for  fifteen  cents  a  gallon,  perhaps  less.  On 
the  other  hand,  if  we  substitute  the  best  and  hardest  asphaltum 
for  all  or  a  portion  of  the  varnish  resins  in  an  oleo-resinous  var- 
nish, particularly  one  containing  considerable  oil,  we  find  that 
such  a  varnish  is  very  slow  to  dry,  and  if  we  accelerate  the  drying 
by  lead  and  manganese  driers,  we  are  liable  to  add  so  much  drier 
that  the  varnish  is  shortly  destroyed  by  their  excess.  But  if  we 
make  such  a  varnish  and  resolutely  give  it  time  enough  to  dry,  we 
find  it  to  be  a  material  of  the  highest  excellence.  Asphaltum  seems 
to  be  between  soft  bituminous  coal  on  the  one  hand  and  liquid 
petroleum  on  the  other.  The  hardest  varieties  are  the  Egyptian 
and  that  known  as  gilsonite,  which  comes  from  Utah.  These  are 
so  hard  that  they  are  very  brittle,  easily  powdered,  and  at  ordinary 
temperatures  the  pieces  have  no  more  tendency  to  stick  together 
than  pieces  of  coal.  Trinidad  asphaltum,  on  the  other  hand, 
contains  so  much  mineral  oily  matter  that  pieces  which  are  pressed 
together  readily  though  slowly  unite,  and  if  a  barrel  of  it  is  laid 
on  its  side  with  the  head  removed  the  asphalt  will  in  time  flow 
out  of  the  barrel.  It  has  about  the  consistency  of  soft  rosin. 
Many  intermediate  grades  are  found  and  also  some  which  are  even 
softer  than  Trinidad,  shading  off  indeed  into  heavy  petroleum. 
From  some  of  these  heavy  mineral  oils,  notably  those  from  Cali- 
fornia, a  residue  from  distillation  is  obtained  very  much  like  the 
natural  soft  asphalts. 

Maltha. — This  residue  is  known  as  maltha,  a  Greek  name  for 
soft  asphaltums,  and  is  of  varying  consistency,  according  to  the 
temperature  at  which  the  distillation  has  stopped,  and  which  is 
varied  according  to  the  use  to  be  made  of  the  residue. 

P.  &  B.  Paint. — In  1886  a  patent  was  issued  to  Pearce  & 
Beardsley,  two  citizens  of  California,  for  a  paint  or  varnish  made 
by  dissolving  this  maltha  in  bisulphide  of  carbon,  a  preparation 


SPIRIT   VARNISHES. 

which  attained  a  considerable  degree  of  popularity  under  the 
name  of  P.  &  B.  paint.  Bisulphide  of  carbon  is  a  volatile 
liquid  which  has  the  singular  property  of  thinning  maltha  very 
rapidly,  so  that  a  small  quantity  of  it  produces  as  great  an  effect 
in  making  the  compound  fluid  as  several  times  as  much  spirit  of 
turpentine  would  have.  Hence  a  varnish  can  be  made  in  this 
way  which  is  almost  all  solid  matter,  and  a  much  thicker  layer 
can  be  applied  than  of  any  other  material.  This  is  in  itself  an 
advantage,  but  it  is  accompanied  with  the  disadvantages  that  the 
compound  easily  thickens  by  the  spontaneous  evaporation  of  even 
a  small  amount  of  the  thinning  material,  and  also  that  the  vapor 
is  highly  poisonous  and  explosive.  It  has,  in  spite  of  these  draw- 
backs,, proved  useful  for  many  purposes.  All  these  soft  asphalts 
owe  their  flexibility  to  the  mineral  oily  matter  which  they  contain, 
and  retain  it  if  kept  in  masses  of  considerable  thickness,  for  exam- 
ple, in  street  pavements  and  the  like;  but  when  made  into  varnish 
and  spread  out  in  a  thin  film,  the  ingredient  which  gives  them 
flexibility  is  absorbed  by  and  passes  off  in  the  air  and  rain,  and 
the  earthy  constituent  alone  is  left,  without  coherence,  which 
becomes  a  powder  and  falls  off.  If  we  start  with  a  hard  asphal- 
tum  like  gilsonite,  we  find  it  necessary  to  add  to  it  something  to 
make  it  coherent  and  elastic. 

Permanently  Elastic  Asphaltum  Varnish. — This  may  be  done 
by  dissolving  it  in  linseed-oil,  and  this,  unlike  the  mineral  oil  of 
the  soft  asphalt,  is  permanent,  and  a  film  of  such  a  varnish  retains 
its  elasticity  as  well  as  one  made  from  oil  and  the  best  varnish 
resins.  Varnishes  may  be  made  in  this  way  of  hard  asphaltum 
and  hard  varnish  resins  with  linseed-oil,  which  have  fine  lustre  and 
extraordinary  durability.  They  are  usually  rather  slow  to  dry, 
but  this  is  less  marked  than  when  asphaltum  alone  is  used  with 
the  oil.  What  is  commonly  sold  as  asphaltum  varnish  is  a  solu- 
tion of  asphaltum  in  turpentine  or  benzine,  mixed  with  a  varying 
amount  of  quick-drying  varnish,  usually  rosin  varnish,  but  as- 
phaltum varnishes  differ  greatly  in  quality  and  price.  Some- 
important  uses  of  asphaltum  will  be  described  in  later  chapters. 


CHAPTER  XI. 

PYROXYLIN  VARNISHES. 

IT  has  long  been  known  that  when  cotton  fibre  (or  in  fact 
any  form  of  cellulose,  as  woody  fibre  in  general  is  called)  is 
immersed  in  nitric,  or,  better,  in  a  mixture  of  nitric  and  sulphuric 
acids,  for  a  very  short  time,  and  then  removed  and  well  washed, 
it  is  found  to  have  undergone  a  chemical  change,  although  its 
outward  appearance  is  the  same  as  before.  One  of  the  most 
conspicuous  things  about  this  change  is  that  while  before  it  was 
very  combustible,  afterward  it  became  highly  explosive;  the 
explosive  thus  made  is  called  guncotton.  Before  nitrating, 
the  cotton  or  other  fibre  is  insoluble  in  almost  every  known 
liquid;  afterward  it  is  easily  soluble  in  various  alcoholic  and 
ethereal  solvents.  Cotton  -  thus  treated  is  also  called  pyroxylin, 
nitrocellulose,  and  soluble  cotton,  as  well  as  guncotton,  and 
may  be  made  of  a  considerable  variety  of  composition,  accord- 
ing as  it  has  been  more  or  less  acted  on  by  the  acid.  A  suitable 
compound  of  this  sort,  dissolved  in  a  mixture  of  ethyl  alcohol 
and  ether,  is  the  collodion,  or  "liquid  court-plaster/'  of  the 
pharmacists,  which,  on  being  applied  to  wounds,  dries  almost 
instantly  and  forms  a  film  like  an  artificial  skin,  which  protects 
from  dirt  and  infection.  This  is  probably  the  earliest  use  of  a 
pyroxylin  varnish,  and  is  still  an  important  one. 

The  commercial  use  of  pyroxylin  lacquers  for  adorning  and 
protecting  manufactured  articles  is  a  subject  of  interest  and 
importance.  The  writer  has  had  no  experience  with  these  var- 
nishes, but  is  fortunately  able  to  supply  the  deficiency  by  the 
aid  of  his  friend,  Mr.  E.  D.  Williams,  Superintendent  of  the 
Celluloid  Zapon  Company  of  Milburn,  N.  J.,  the  largest  and 

112 


PYROXYLIN   VARNISHES. 

most  important  manufacturers  of  these  products  in  this  or  any 
other  country;  hence  the  reader  may  accept  with  confidence  the 
following  outline  of  the  subject: 

Collodion. — The  earliest  use  in  the  arts  of  a  pyroxylin  var- 
nish was  in  the  application  of  collodion  to  photographic  plates; 
when  the  wet  method  of  preparing  and  using  such  plates  was 
in  vogue  collodion  was  an  important  part  of  the  photographer's 
outfit;  and  although  dry  plates  are  made  without  its  use,  it  is 
more  used  in  photography  than  ever,  as  it  is  now  used  for  making 
the  flexible  films  used  in  "Kodak"  and  other  film  cameras. 

Kodak  Films. — For  this  purpose  a  methyl- alcohol  solution 
is  used.  The  Eastman  Kodak  Company  is  said  to  make  a  solu- 
tion as  follows:  97  percent,  methyl  alcohol,  65  parts;  amyl  alcohol, 
25  parts;  amyl  acetate,  10  parts.  To  a  gallon  of  this  solvent 
1 6  ounces  of  pyroxylin  is  added.  This  varnish  is  spread  on 
long  glass  plates  previously  coated  with  a  thin  solution  of  paraffin 
to  prevent  adhesion.  This  work  must  be  performed  in  a  room 
the  air  of  which  is  as  dry  as  possible,  to  prevent  the  hygroscopic 
wood-alcohol  from  taking  up  water.  The  air  is  dried  by  passing 
it  through  refrigerating  coils,  by  which  means  the  moisture  is 
precipitated;  when  the  air  subsequently  rises  in  temperature 
it  is  dry  in  the  sense  that  it  will  no  longer  give  up  moisture. 
The  films  are  finally  stripped  from  the  glass  plates  and  coated 
with  the  sensitive  emulsion,  thus  producing  a  flexible  sensitive 
plate  which  will  withstand  the  various  chemicals  used  in  photo- 
graphic developers.  A  thin  solution  of  pyroxylin  in  wood- 
alcohol  or  other  solvents  is  also  often  used  to  flow  over  the  devel- 
oped negative  to  protect  the  gelatine  film  from  being  scratched 
or  absorbing  moisture.  Many  photographers  use  this  same 
solution  to  varnish  their  finished  pictures.  When  thus  protected, 
negatives  and  pictures  can  be  handled  with  little  fear  of  injury, 

As  soon  as  pyroxylin  varnishes  came  into  extensive  use  for 
photographic  purposes,  other  uses  suggested  themselves;  but 
in  order  to  adapt  them  for  use  on  metals  and  wood,  solvents 
had  to  be  found  which  would  not  dry  too  quickly  or  take  up 
moisture  from  the  air  and  thus  cause  precipitation  of  the 


H4  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

pyroxylin.  Among  the  solvents  which  were  early  discovered 
were  nitrobenzole  ("oil  of  mirbane")  and  acetic  ether,  both  of 
which  were  used  in  conjunction  with  methyl  alcohol,  and  as  the 
alcohol  evaporated  first,  the  resulting  film,  even  though  it  turned 
white,  would  eventually  clear  up,  as  the  slower-drying  solvents 
remained  until  after  the  water  had  evaporated  and  redissolved 
any  pyroxylin  which  might  have  become  precipitated. 

As  these  mixed  solvents  had  many  objectionable  qualities, 
and  the  demand  for  a  lacquer  suitable  for  polished  metallic 
surfaces  increased,  a  great  deal  of  research  work  was  done  to 
find  suitable  solvents  for  nitrocellulose  which  would  dissolve 
it  perfectly  and  make  a  lacquei  which  would  dry  slowly  enough 
in  the  air  to  give  a  uniformly  smooth,  clear,  transparent  film 
which  would  not  impair  the  lustre  of  these  polished  surfaces 
and  would  adhere  to  them.  Camphor  and  all  crystalline  sub- 
stances had  to  be  eliminated,  as  they  would  recrystallize  on 
drying  and  give  a  dull  finish. 

Solvents. — Among  the  solvents  which  we  find  mentioned  in 
the  early  history  of  the  subject  are  acetone,  nitrate  of  methyl, 
butyric  ether,  valeric  ether,  benzoic  ether,  formic  ether,  salicylate 
of  methyl,  formate  of  amyl,  acetate  of  amyl,  butyrate  of  amyl, 
valerianate  of  amyl,  sebacylic  ether,  oxalic  ether,  and  amylic 
ether.  Few  of  these  have  been  found  to  be  of  any  practical 
use  except  the  amyl  compounds,  which  are  formed  by  the  action 
of  various  acids,  as  formic,  acetic,  etc.,  on  amyl  alcohol  (fusel- 
oil)  and  distilling  in  the  presence  of  sulphuric  acid.  These 
compound  ethers  have  proved  to  be  exceedingly  useful  in  making 
pyroxylin  varnishes,  as  they  are  non-hygroscopic  and  flow  out 
perfectly,  dry  readily,  and  are  not  injurious  to  the  health  of  the 
workmen.  Acetate  of  amyl  has  been  most  largely  used  and 
is  at  the  present  time  in  such  demand  for  this  purpose  that  the 
supply  in  this  country  and  Europe  does  not  nearly  reach  the 
'requirements;  while  a  few  years  ago  fusel-oil,  from  which  it  is 
made,  was  a  waste  product  of  the  alcohol  distilleries,  for  which 
it  was  difficult  to  find  disposal.  Unfortunately  no  practical 
way  has  yet  been  invented  for  making  the  amyl  compounds 


PYROXYLIN   VARNISHES.  115 

synthetically,  and  it  is  impossible  to   obtain  them  except  from 
a  by-product;   so  a  shortage  is  a  natural  result. 

Cellulose. — Another ..  important  question  to  decide  is  what 
form  of  cellulose  shall  be  used  to  give  a  certain  result;  many 
are  used,  such  as  cotton,  both  in  the  fibre  and  as  cotton  waste, 
etc.,  straw,  pith,  flax,  paper,  ramie,  etc.;  the  choice  among  these 
has  its  own  influence;  and  even  the  thickness  of  the  fibre  will 
Cause  one  lot  of  cotton  to  entirely  disintegrate  in  tlje  acid  mixture, 
while  a  different  fibre  will  nitrate  and  remain  as  strong  as  the 
original. 

Nothing  but  these  pyroxylin  lacquers  has  successfully  an- 
swered the  requirements  of  the  enormous  factories  which  turn 
out  building  hardware,  gas  and  electric  fixtures,  lamps,  all 
sorts  of  polished  brass,  silver  and  silver-plated  articles,  all  of 
which  easily  tarnish  and  must  be  protected. 

Colored  Lacquers. — These  lacquers  are  also  colored  by  dis- 
solving various  dyes  in  the  pyroxylin  solution,  and  are  then 
used  for  decorating  metals  and  glass;  the  largest  use  of  these 
colored  lacquers  is  probably  for  coloring  electric-light  bulbs. 

Enamels. — Beautiful  enamels  are  also  made  by  grinding 
pigments  in  these  varnishes;  some  difficulty  is  experienced  with 
heavy  pigments,  which  are  hard  to  keep  in  suspension;  but  the 
lighter  ones  will  remain  a  long  time  without  settling.  Velvet 
blacks  are  especially  used  on  ornamental  metal  work;  also  gray 
colors  are  coming  into  use. 

Resins  Used  with  Pyroxylin. — Pyroxylin  varnishes  are  greatly 
improved  for  use  with  the  brush  by  adding  to  them  various  resins, 
such  as  shellac,  manila,  sandarac,  damar,  mastic,  tolu,  benzoin, 
etc.  These  give  an  increased  body  to  the  solution  without 
increasing  its  viscosity  and  thus  enable  us  to  get  a  heavier  coat- 
ing without  changing  the  flowing  qualities  of  the  varnish.  The 
most  serious  difficulty  experienced  with  these  solutions  is  due 
to  the  fact  that  most  resins  contain  acids,  and  these  cause  the 
film  to  decompose  so  that  a  polished  metallic  surface  is  liable 
to  darken  after  a  week  or  so,  which  is  a  fatal  objection. 

Thin    Films. — The    great    desire    of    the    pyroxylin-varnish 


Ii6  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

makers  has  always  been  to  get  an  article  which  could  be  applied 
to  wood  in  such  a  way  as  to  compete  with  oleo-resinous  varnishes 
and  paints;  the  great  difficulty  has  been  that  when  pyroxylin 
solution  is  made  up  to  the  consistency  of  these  varnishes,  there 
are  only  about  six  ounces  of  pyroxylin  to  a  gallon  of  solvent; 
when  the  film  dries  the  solvent  evaporates,  and  the  amount  of 
solids  remaining  is  so  small  that  there  is  an  exceedingly  thin 
film,  thus  requiring  many  applications  to  get  a  sufficient  covering; 
while  with  the  oleo-resinous  varnishes  the  contents  which  become 
solid  on  drying  amount  to  three  or  four  (or  more)  pounds  to 
the  gallon  and  the  thickness  of  the  film  is  correspondingly  greater. 

Fillers. — The  best  results  in  the  use  of  these  varnishes  on 
wood  have  been  obtained  by  using  a  pyroxylin  solution  for  a 
filler  which  lays  the  grain  of  the  wood  exceptionally  well,  then 
applying  an  oleo-resinous  varnish  over  this  for  body,  and  finally 
a  finishing  coat  of  pyroxylin  varnish  for  hardness.  This  method 
of  procedure  has  been  used  very  extensively  in  finishing  pencils, 
penholders,  rulers,  hair-brushes,  and  all  sorts  of  small  wood 
articles.  Oleo-resinous  varnishes  require  either  long  drying  or 
baking,  while  the  quick  drying  of  the  solvents  makes  the  pyroxylin 
lacquers  more  desirable  for  some  of  this  work,  especially  as  they 
produce  a  surface  of  unusual  hardness  and  durability. 

Thinness  of  film,  i.e.,  a  lack  of  a  sufficient  amount  of  binding 
material,  prevents  making  paints  for  ordinary  use;  but  10  per 
cent.,  or  thereabouts,  of  pyroxylin  solutions  has  been  added  to 
linseed-oil  paints  with  good  results,  and  many  large  paint  manu- 
facturers are  experimenting  on  this  line. 

Artificial  Leather. — Great  interest  has  been  manifested  in 
the  problem  of  applying  pyroxylin  solutions  to  leather  to  avoid 
cracking  the  enamel,  which  is  so  great  a  disadvantage  of  the 
ordinary  patent-leather  finish.  Every  patent-leather  maker  in 
the  country  has  recently  been  working  on  this  question,  as  rumors 
have  been  rife  that  wonderful  results  have  been  obtained.  As 
this  material  has  been  used  for  years  on  cloth  to  make  a  flexible 
coating  which  will  not  crack  or  deteriorate,  there  seems  to  be 
no  reason  why  it  should  not  be  applied  with  advantage  to  leather; 


PYROXYLIN    VARNISHES.  1 17 

but  as  yet  no  satisfactory  results  have  been  obtained.  It  probably 
must  be  compounded  with  various  fixed  oils  to  give  it  sufficient 
flexibility,  as  is  done  in  the  enamelled-cloth  industries.  In  this 
last-named  work  very  beautiful  results  have  been  reached  by 
embossing  the  coated  cloth  with  all  sorts  of  ornamental  designs 
and  then  embellishing  these  figures  with  various  colors;  such 
products  are  used  for  wall  decoration  and  similar  uses. 

One  of  the  best-known  uses  of  pyroxylin  lacquers  is  its  use 
as  a  medium  for  applying  bronze  and  aluminum  powders;  amyl 
acetate,  which  is  the  chief  solvent,  has  a  pungent  odor  resembling 
bananas,  hence  the  lacquer  used  for  these  bronze  and  aluminum 
paints  has  the  trade  name  of  "banana  liquid."  In  this  way 
the  use  of  pyroxylin  varnish  is  becoming  generally  familiar. 


CHAPTER  XII. 

OIL  PAINTS  AND  PAINTS  IN  JAPAN. 

PAINT  has  been  used  for  decorative  purposes  from  prehistoric 
times,  and  is  so  used  at  the  present  day  by  all  savages  as  well 
as  all  civilized  races.  That  which  makes  paint  decorative  is 
its  color,  and  this  comes  from  the  pigment  which  it  contains. 
Pigments  are  solid  substances,  insoluble  in  the  oil  or  other  liquid 
which  forms  the  fluid  part  of  the  paint  (and  which  is  technically 
called  the  "vehicle"),  and  are  in  the  form  of  a  fine  powder, 
usually  reduced  to  the  desired  fineness  by  grinding,  but  some- 
times, as  in  the  case  of  lampblack,  chemically  deposited  in  a 
form  so  finely  comminuted  as  to  satisfy  the  needs  of  the  paint 
manufacturer. 

Fineness. — In  general  pigments  should  be  so  fine  that  they 
will  pass  through  a  brass  wire  sieve  having  two  hundred  meshes 
to  the  linear  inch;  for  some  uses  pigments  may  answer  which 
are  not  so  fine,  but  in  any  case  should  pass  through  a  screen  of 
one  hundred  meshes  to  the  linear  inch.  In  preparing  these, 
the  substances  of  which  they  are  to  be  made  are  ground  in  burr- 
stone  mills,  sometimes  dry,  sometimes  mixed  with  water;  in  the 
latter  case,  they  may  be  sifted  wet,  but  more  commonly  are 
dried,  crushed,  and  bolted.  The  bolting  process  is  also  applied 
to  dry  ground  pigments.  But  for  cheap  paints  it  is  assumed  to 
be  safe  to  determine  by  trial  how  the  mills  should  be  arranged 
and  then  put  the  material  through  and  use  it  as  it  comes  from 
the  mill  without  any  preliminary  sifting  or  bolting.  The  paint 
manufacturer  who  buys  the  prepared  pigment  has  his  own 
methods  of  testing  for  fineness ;  the  most  common  thing  is  to  rub 

118 


OIL  PAINTS  AND   PAINTS  IN  JAPAN.  H9 

it  on  a  glass  or  porcelain  plate  with  a  palette-knife  side  by  side 
with  a  standard  article.  Practically  nearly  all  selection  of  pig- 
ments is  by  testing  them  against  standard  articles,  chemical 
analysis  being  only  occasionally  resorted  to,  and  then  for  impur- 
ities in  well-known  chemical  substances,  such  as  white  lead. 

It  is  not  the  purpose  of  the  writer  to  go  into  any  elaborate 
account  of  the  various  pigments  because  there  are  now  books 
devoted  to  that  subject  which  treat  it  more  fully  and  with  greater 
knowledge  than  he  can.  But  the  action  of  pigments  on  the 
vehicles  or  liquids  in  which  they  are  mixed  is  a  proper  subject 
to  consider  here,  and  while  it  cannot  be  discussed  in  a  very 
thorough  manner,  it  is  desired  to  say  something  about  it,  and 
it  is  desirable  to  first  say  something  about  the  most  common 
and  important  pigments.  All  very  light  colors  have  white  as 
their  foundation  or  principal  ingredient,  and  white  pigments 
are  limited  in  number  to  a  few  substances,  the  chief  being  white 
lead  and  white  zinc. 

White  Lead. — White  lead,  when  made  by  what  is  known  as  V/ 
the  Dutch  process,  as  most  of  it  is,  consists  of  a  mixture  of  two 
or  three  parts  of  carbonate  and  one  part  of  hydrate  of  lead.  It 
is  made  from  metallic  lead,  which  is  cast  into  plates  of  irregular 
form,  a  few  inches  in  diameter,  termed  " buckles,"  which  are 
suspended  in  earthern  jars  over  dilute  acetic  acid  and  kept  in  a 
warm  place  where  they  will  be  exposed  to  air  containing  a  large 
amount  of  carbonic  acid,  usually  by  burying  the  jars  in  ferment- 
ing tan-bark.  The  acid  attacks  the  lead,  forming  acetate  of 
lead ;  this  is  decomposed  by  the  carbonic  acid,  making  carbonate, 
and  the  acetic  acid  set  free  attacks  a  fresh  portion  of  metallic 
lead,  and  so  on.  The  Bolognese  MS.,  written  early  in  the 
fifteenth  century,  gives  the  following  formula:  "Take  lead  in 
plates  and  suspend  them  over  the  vapor  of  very  strong  vinegar 
in  a  vase,  which  after  being  luted  must  be  placed  in  dung  for 
two  months,  then  scrape  away  the  matter  that  you  will  find  upon 
the  plates,  which  is  the  white  lead.  Do  this  until  the  plates 
are  consumed."  So  that  the  process  has  remained  unchanged 
at  least  five  hundred  years,  perhaps  five  times  that.  In  fact,  an 


120  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

almost  identical  formula  is  given  by  Dioscorides,  in  the  first 
century  B.C. 

Sulphate  of  Lead.  —  There  is  some  white  lead  made  of  a 
different  composition,  namely,  the  sulphate.  This  is  used  es- 
pecially as  a  filler  or  surfacing  material  for  fine  cardboard,  as 
it  does  not  discolor  with  the  heat  of  the  calendering- rolls.  White 
lead  as  commonly  made  is  not  chemically  an  extremely  stable 
compound.  The  carbonates  are  all  rather  easily  decomposed, 
and  the  hydrate  is  in  a  form  which  will  unite  with  acid  substances 
with  great  readiness.  Owing  to  this,  we  find  that  in  time  (not 
very  rapidly)  it  combines  with  linseed-oil  and  more  rapidly  with 
varnishes,  some  of  which  contain  a  little  acid.  Like  all  the 
lead  compounds,  it  is  of  high  specific  gravity,  and  a  larger  amount 
by  weight  of  white  lead  than  of  any  other  pigment  can  be  com- 
bined with  a  given  weight  of  oil. 

Paste  White  Lead. — It  is  sometimes  sold  as  a  dry  powder, 
but.  more  commonly  ground  with  10  per  cent,  of  its  weight  of 
raw  oil  as  white- lead  paste.  It  is  generally  believed  that  if  it 
has  once  been  dried  it  cannot  then  be  made  into  as  fine  a  paint 
as  when  mixed  with  oil  to  a  paste  in  the  first  place;  for  it  has 
been  found  that  white  lead  wet  with  water,  in  which  form  it  comes 
from  the  washing-vats  where  the  acetic  acid,  etc.,  are  removed, 
can  be  put  into  a  steam-heated  agitator  or  mixer  with  some  oil, 
and  the  oil  will  displace  the  water,  because  there  is  more  attrac- 
tion between  the  lead  and  oil  than  between  the  lead  and  water; 
hence  we  find  traces  of  water  in  paste  lead. 

White  Zinc. — White  zinc  is  the  oxide  of  zinc,  and  is  made  in 
metallurgical  works  by  burning  zinc  in  air.  It  is  not  inferior 
in  whiteness  to  white  lead — in  fact  it  is  commonly  thought  to 
be  whiter — but  it  is  not  so  opaque,  and  more  coats  of  zinc  paint 
are  necessary  to  get  a  given  effect  over  a  dark  background  then 
of  lead.  It  is  not  very  readily  attacked  by  the  acids  in  linseed- 
oil,  but  both  lead  and  zinc  are  to  some  extent  so  affected. 

Lithopone. — Another  white  paint  containing  zinc  is  known 
by  the  trade  name  of  lithopone;  it  is  essentially  the  sulphide 
of  zinc  mixed  with  a  variable  percentage  of  barytes.  White 


OIL  PAINTS  AND  PAINTS  IN  JAPAN.  121 

lead  and  white  zinc  are  practically  the  only  white  pigments  used 
in  oil  or  varnish ;  other  white  powders,  such  as  powdered  gypsum 
(sold  under  the  name  of  terra  alba),  whiting  (which  is  powdered 
chalk — carbonate  of  lime),  kaolin,  and  barytes,  are  used  as 
adulterants,  though  they  are  actually  pigments  of  value  in  paints 
ground  in  watery  vehicles.  The  reason  is  that  they  are  in  their 
nature  transparent  and  appear  white  just  as  glass  ground  to 
a  powder  does,  but f  when  mixed  with  oil  the  refractive  index  of 
the  oil  is  nearly  that  of  those  pigments  and  so  they  become  trans- 
parent again.  Watery  vehicles,  such  as  are  used  in  water-colors, 
fresco  paints,  and  kalsomine,  evaporate  and  leave  them  to  show 
their  power  of  reflecting  white  light.  So  that  whiting,  which 
was  a  favorite  pigment  with  the  ancient  painters,  who  used  a 
watery  solution  of  glue,  or  of  albumen,  as  vehicle,  is  of  very  little 
value  to  the  oil  painter,  and  it  is,  moreover,  an  alkaline  substance 
which  attacks  and  after  a  time  destroys  the  oil.  Barytes  is 
perfectly  neutral;  it  is  sulphate  of  barium,  a  most  unchangeable 
salt.  When  chemically  precipitated  it  is  known  as  blanc  fixe, 
and  this  is  made  as  a  by-product  in  some  chemical  factories; 
being  amorphous — while  ordinary  barytes  is  crystalline — and 
extremely  fine,  it  is  somewhat  better  than  any  of  the  other  adul- 
terants, and  possibly  has  a  little  value  of  its  own. 

Barium  Sulphate  and  Carbonate. — Barium  carbonate  is  also 
used  as  an  adulterant;  it  has  an  advantage  over  the  use  of  the 
sulphate  in  that  it  is  soluble  in  the  same  acids  which  dissolve 
lead  carbonate  and  is  on  that  account  liable  to  be  overlooked 
in  a  chemical  analysis ;  if  fraud  is  designed,  it  is,  therefore,  more 
likely  to  escape  notice,  and  it  is  here  mentioned  that  analysts 
may  look  for  it. 

Value  of  White  Under-body.  —  These  white  pigments,  zinc 
and  lead,  are  the  base  of  all  light -colored  paints,  for  it  is  impos- 
sible to  make  a  light -colored  paint  out  of  dark-colored  materials. 
They  are  also  used  to  make  a  white  foundation  on  which  other 
colors  are  overlaid.  This  is  a  practice  of  great  antiquity  and 
is  followed  not  only  in  the  painting  done  by  artists  but  also  in 
not  a  little  technical  work,  using  somewhat  transparent  colors 


122  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

over  the  white,  which  then  serves  as  a  sort  of  mirror,  reflecting 
the  light  which  penetrates  to  it  outward  through  the  translucent 
outer  coat  again,  and  thus  producing  a  warm  and  brilliant  effect 
to  be  had  in  no  other  way.  Eastlake  says  that  "it  is  an  important 
fact  in  painting  that  a  light,  warm  color,  passed  in  a  semi-trans- 
parent state  over  a  dark  one  produces  a  cold,  bluish  hue,  while 
the  operation  reversed  produces  extreme  warmth.  The  secret 
of  Van  Eyck  and  his  contemporaries  is  always  assumed  to  con- 
sist in  the  vehicle  he  employed,  but  a  far  more  important  con- 
dition of  the  splendor  in  the  works  of  those  masters  was  the 
careful  preservation  of  internal  light  by  painting  thinly,  but 
ultimately  with  great  force,  on  white  grounds."  This  is  not  a 
new  observation,  though  so  true  and  important  as  to  bear  repeat- 
ing. Aristotle  made  the  same  remark:  "White  surfaces,  as  a 
ground  for  colors,  have  the  effect  of  making  the  pigments  appear 
in  greater  splendor."  Again  Aristotle  says  ("De  Sensu  et  Sen- 
sibi"):  "Another  mode  in  which  the  effect  of  colors  is  exhibited  is 
when  they  appear  through  each  other,  as  painters  employ  them 
when  they  glaze  a  color  over  a  lighter  one,  just  as  the  sun,  which 
is  iii  itself  white,  assumes  a  red  color  when  seen  through  darkness 
and  smoke.  This  operation  also  ensures  a  variety  of  colors,  for 
there  will  be  a  certain  ratio  between  those  which  are  on  the  sur- 
face and  those  which  are  in  depth."  Compare  this  with  Leonardo 
Da  Vinci,  on  Painting,  Chapter  CCXXXIII:  "When  a  trans- 
parent color  is  laid  upon  another  of  a  different  nature,  it  produces 
a  mixed  color,  different  from  either  of  the  simple  ones  which 
compose  it.  This  is  observed  in  the  smoke  coming  out  of  a 
chimney,  which,  when  passing  before  the  black  soot,  appears 
bluish,  but  as  it  ascends  against  the  blue  of  the  sky  it  changes 
its  appearance  into  a  reddish  brown."  It  might  be  inferred 
that  Leonardo  had  read  Aristotle,  and  no  doubt  he  had,  for  he 
was  a  man  of  much  learning  and  not  only  one  of  the  greatest 
painters  but  also  one  of  the  greatest  men  who  ever  painted;  but 
it  is  to  be  observed  that  not  only  the  foregoing,  but  about  every 
other  important  theorem  on  the  subject,  may  be  found  in  his 
book.  In  regard  to  the  same  thing  Pliny  (1.  xxxv,  c.  18)  says  of 


OIL  PAINTS  AND   PAINTS  IN  JAPAN.  .123 

Apelles:  "No  one  was  able  to  imitate  one  thing  in  that  he  spread 
the  varnish  over  his  completed  work  so  thin  that  it  brought  out 
the  brilliancy  of  the  colors  by  reflection  and  protected  it  from 
dust  and  dirt.  It  seemed  to  the  beholder  to  be  directly  from 
the  hand  of  the  artist.  And  this  with  good  reason,  for  the  bril- 
liancy of  the  color  could  not  offend  the  keenest  eye,  just  like 
looking  through  a  piece  of  mica  from  a  distance,  and  this  thing 
secretly  gave  darkness  to  the  too-bright  colors." 

So  it  appears  that  there  are  both  artistic  and  traditional 
reasons  for  the  very  general  use  of  white  (especially  white  lead) 
as  a  priming  coat,  and  perhaps  the  tradition  is  a  strong  reason 
for  the  general  belief  in  it,  especially  when  its  color  will  finally 
be  of  no  effect. 

Importance  of  Fine  Grinding. — In  this  connection  it  should 
be  pointed  out  that  when  it  is  desired  to  secure  this  brilliancy 
by  superimposing  colors  on  a  light  ground,  their  clearness  must 
be  greatly  enhanced  by  having  the  pigments  ground  to  the  last 
degree  of  fineness.  This  was  well  known  to  the  great  masters 
in  painting,  who  had  them  ground  most  carefully  in  their  own 
laboratories.  Cennini  (ch.  36)  says:  "To  grind  properly,  pro- 
cure a  slab  of  porphyry  which  is  strong  and  firm.  There  are 
many  kinds  of  stone  for  grinding  colors,  as  porphyry,  serpentine, 
and  marble.  The  serpentine  is  a  soft  stone,  and  is  not  good; 
marble  is  worse,  that  is,  softer;  porphyry  is  the  best  of  all,  and 
if  you  procure  a  slab  very  well  polished,  it  will  be  better  than 
one  with  less  polish.  Take  another  stone,  also  of  porphyry, 
smooth  on  one  side,  and  raised  on  the  other,  in  the  shape  of  a 
porringer  and  half  the  height  of  one,  of  such  a  form  that  the 
hand  may  hold  and  guide  it  at  pleasure.  Then  take  some  of 
the  color  and  put  it  on  the  slab,  and  with  that  stone  which  you 
hold  in  your  hand  break  the  pigment  into  small  pieces.  Put 
some  clean  water,  either  from  a  river,  a  fountain,  or  a  well,  to 
the  color  and  grind  it  well  for  half  an  hour,  or  an  hour,  or  as 
long  as  you  please;  but  know  that  if  you  were  to  grind  it  for 
a  year,  so  much  the  better  would  be  the  color.  Then  take  a 
flat  piece  of  wood,  part  of  which  is  pared  thin  like  the  blade  of 


124  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

a  knife,  and  with  this  blade  collect  the  color  neatly;  keep  it 
liquid  and  not  too  dry,  that  it  may  flow  well  on  the  stone  and 
be  thoroughly  ground;  then  collect  it  carefully.  Put  it  then 
into  a  small  vase  and  pour  water  on  it  till  the  vase  is  full,  and 
in  this  manner  keep  it  always  soft  and  well  covered  from  the 
dust,  and  from  all  other  dirt,  that  is,  in  a  little  box  adapted  to 
hold  vessels  of  liquor."  Again,  when  speaking  of  vermilion,  he 
says:  "Put  this  then  upon  the  slab  above  mentioned,  grinding 
it  with  clean  water  as  much  as  you  can — if  you  were  to  grind 
it  for  twenty  years,  it  would  be  but  the  better  and  more  perfect." 
No  care  was  too  great  for  the  proper  mechanical  preparation 
of  pigments,  in  his  opinion;  note  the  use  of  the  wooden  palette- 
knife,  to  avoid  contact  with  iron — a  very  general  precaution. 
And  after  giving  long  and  elaborate  directions  for  preparing 
ultramarine  (the  natural,  not  the  artificial),  he  adds:  "You 
must  know  also  that  it  (the  care  of  preparation)  is  rather  the 
acquirement  of  youth  than  that  of  men,  because  they  remain 
continually  in  the  house,  and  their  hands  are  more  delicate. 
Beware  especially  of  preparing  it  in  old  age."  Again  and  again 
he  insists  on  having  the  best  materials;  thus  in  ch.  96:  "It  is 
usual  to  adorn  walls  with  gilded  tin,  because  it  is  less  expensive 
than  gold.  Nevertheless,  I  give  you  this  advice,  that  you  en- 
deavor always  to  use  fine  gold  and  good  colors,  particularly  in 
painting  representations  of  Our  Lady.  And  if  you  say  that  a 
poor  person  cannot  afford  the  expense,  I  answer  that  if  you  work 
well  (and  give  sufficient  time  to  your  work)  and  paint  with  good 
colors,  you  will  acquire  so  much  fame  that  from  a  poor  person 
you  will  become  a  rich  one,  and  your  name  will  stand  so  high 
for  using  good  colors  that  if  some  masters  receive  a  ducat  for 
painting  one  figure,  you  will  certainly  be  offered  two,  and  your 
wishes  will  be  fulfilled;  according  to  the  old  proverb,  good  work 
good  pay.  And  even  should  you  not  be  well  paid,  God  and  Our 
Lady  will  reward  you  soul  and  body  for  it."  Such  are  the 
opinions  set  down  in  the  oldest  treastise  on  painting;  though  six 
centuries  old,  they  are  worthy  of  remembrance. 

Chrome    Yellow. — The   more  important  of  the  yellow  pig- 


OIL  PAINTS  AND   PAINTS  IN  JAPAN.  125- 

ments  are  chrome  yellow  and  cadmium  yellow.  The  chrome 
yellows  are  made  in  three  shades,  pale,  medium,  and  deep.  Of 
these  the  latter  is,  or,,  should  be,  pure  chromate  of  lead.  It  is 
orange  in  color.  The  medium  chrome  is  the  same  with  some 
carbonate  or  sulphate  of  lead,  and  the  pale  has  still  more  of 
the  carbonate  or  sulphate.  The  chromate  is  a  chemical  pre- 
cipitate, and  in  making  the  lighter  shades  carbonate  or  sulphate 
of  lead  is  precipitated  at  the  same  instant,  thus  securing  a  more 
perfect  mixture  than  can  otherwise  be  had,  and  more  brilliant 
color.  The  chrome  yellows  when  exposed  to  the  weather  are 
somewhat  inclined  to  fade,  but  they  are  colors  of  great  beauty 
and  are  very  opaque.  Some  of  the  ochres  are  yellow  also,  but 
not  so  pure  a  color;  they  are,  however,  permanent,  and  are 
extensively  used,  especially  in  mixtures.  Cadmium  yellow  is 
both  brilliant  and  permanent,  and  is  an  excellent  paint  where 
the  cost  does  not  prevent  its  use;  but  it  is  expensive.  The 
chromate  of  strontium  is  a  pale  yellow  of  great  brilliancy,  but 
transparent,  so  that  it  can  be  used  only  as  a  glazing  color,  usually 
over  chrome  yellow;  it  is  of  the  highest  degree  of  permanence. 
Yellow  is  not  infrequently  added  to  dark  colors  to  give  them 
a  warm  tone,  and  is  often  present  in  considerable  amount  where 
the  untrained  eye  does  not  detect  it  at  all.  It  has  a  most  agree- 
able effect  in  these  mixtures. 

Chrome  Green. — The  most  important  green  is  chrome  green,, 
which  is  a  mixture  of  chrome  yellow  and  Prussian  blue,  the 
latter  being  chemically  a  ferrocyanide  of  iron.  Each  of  these 
pigments  separately  has  great  "body"  or  opacity,  and  their 
mixture  is  unsurpassed  in  this  respect  except  by  some  of  the 
blacks.  The  different  shades  of  this  color  are  made  in  the  same 
way  as  the  chrome  yellows. 

Paris  Green. — A  much  more  transparent  color,  but  of  extra- 
ordinary brilliancy,  is  Paris  green,  as  it  is  called  in  this  country, 
known  as  emerald-green  in  England,  and  by  various  names  in 
Germany.  It  is  an  aceto-arsenite  of  copper,  and  not  a  very 
satisfactory  paint,  but  it  is  of  unequalled  color,  which  insures, 
a  considerable  use. 


126  TECHNOLOGY  OP   PAINT  AND    VARNISH. 

Chrome-oxide  Green. — There  is  another  kind  of  chrome 
green,  namely,  the  green  oxide,  which  is  prepared  both  in  the 
hydrated  and  the  anhydrous  state,  the  latter  being  preferred 
on  all  accounts.  It  is  one  of  the  most  permanent  and  indestruc- 
tible of  colors,  and  is  quite  opaque,  but  rather  dull  in  color.  It 
is  often  said  that  this  is  the  only  pigment  to  which  the  name 
of  chrome  green  should  be  applied,  but  in  fact  the  name  is  ap- 
propriated commercially  by  the  chrome-yellow-Prussian-blue 
compound,  and  in  this  country,  at  least,  it  has  been  found  prudent 
to  designate  the  other  as  chrome-oxide  green.  It  is  rather  expen- 
sive and  not  brilliant  in  color,  but  of  a  color  which,  though  rather 
cold,  is  considerably  liked.  It  is  a  very  valuable  pigment.  Zinc 
green  and  cobalt  green  are  the  same,  a  compound  of  zinc  and 
cobalt,  of  fine  color  and  extreme  permanence.  Its  cost  is  the 
only  objection  to  it. 

Blue  Pigments. — Only  two  or  three  blue  pigments  are  in 
common  use :  Prussian  or  Chinese  blue,  a  chemically  prepared 
ferrocyanide  of  iron,  a  dark  blue  pigment,  quite  opaque,  not 
extremely  permanent;  and  ultramarine,  a  color  originally  had 
from  a  mineral — lapis  lazuli — but  now  made  artificially  in  great 
quantities.  This  is  moderately  permanent,  not  very  deep  in 
color,  and  constitutes  most  of  the  blue  used  in  ordinary  paints. 
In  one  respect  it  is  an  exception  to  a  general  rule,  in  that  it  is 
not  improved  but  rather  injured  by  excessive  grinding.  It  is 
as  though  the  color  were  on  the  outside  of  the  particles  as  they 
come  from  the  ultramarine  manufactory  and  as  if,  on  grinding, 
these  particles  were  broken  up  and  the  color  injured  by  bringing 
into  view  the  interior  portions  of  the  particles. 

Cobalt  blue  is  a  compound  of  cobalt  and  alumina,  a  fine 
color  of  the  highest  permanence,  but  rather  costly.  It  is  used 
to  some  extent  for  high-class  work,  but  is  rather  to  be  regarded 
as  an  artist's  color. 

Vermilion. — No  doubt  the  most  important  of  the  red  pig- 
ments are  the  iron  oxides,  but  as  these .  are  not  pure  in  color, 
we  may  first  mention  vermilion,  which  is  an  artificial  sulphide 
of  mercury,  of  a  beautiful  scarlet  color;  it  has  always  been,  in 


OIL  PAINTS  AND   PAINTS  IN  JAPAN.  127 

spite  of  its  rather  high  price,  a  favorite  pigment;  it  is  not  very 
permanent.  It  is  known  in  this  country  as  English  vermilion, 
most  of  it  being  imported  from  England;  formerly  it  was  called 
Chinese  vermilion  but  that  which  comes  from  China  does  not 
appear  to  be  equal  to  the  English.  What  is  known  as  American 
vermilion  is  made  by  precipitating  red  coal-tar  colors  on  red 
/lead,  orange  lead,  or  barytes,  or  on  sulphate  or  carbonate  of 
lead,  and  there  are  a  large  number  of  reds  used  in  the  paint 
trade  which  are  made  from  the  coal-tar  dyes,  some  of  which, 
unlike  American  vermilion,  are  very  fast  to  light,  but  they  are 
not  of  great  opacity,  being  rather  to  be  classed  as  lakes.  It 
may  be  remarked  for  the  benefit  of  such  readers  as  are  not 
familiar  with  these  matters  that  lakes  are  compounds  of  the 
coloring  matters  of  dyes  with  a  mineral  substance,  such  as  lead 
or  alumina;  one  of  the  best  known  being  carmine,  made  from 
cochineal,  certainly  the  most  beautiful  red  color  that  has  ever 
been  seen  and  which  is  used  in  painting,  especially  in  carriage - 
painting,  almost  as  much  as  ever,  in  spite  of  the  fact  that  it  is 
not  permanent. 

Red  lead  is  also  used,  but  the  consideration  of  this  substance 
will  be  deferred  to  a  later  chapter,  since  it  is  chiefly  used  as  a 
protective  paint  for  iron  and  steel.  The  iron  oxides  are  also  so 
used,  but  their  chief  use  is  in  making  cheap  paints  for  wooden 
surfaces,  for  which  they  are  well  adapted.  Most  of  them  are 
quite  permanent  in  color ;  and  though  dull,  they  are  of  rather 
pleasing  colors,  and  have  great  covering  power  or  opacity.  There 
are  essentially  two  kinds  of  iron  oxides,  the  anhydrous  sesquioxide 
and  the  same  hydrated.  They  exist  in  nature,  the  first  as  the 
mineral  called  hematite,  the  second  as  limonite.  The  former 
when  powdered  is  dark  red,  the  latter  yellowish  red.  There 
are  indeed  other  oxides  of  iron,  notably  the  magnetic  oxide, 
which  is  black  in  color,  but  it  is  not  used  as  a  pigment. 

Hematite  occurs  pure  in  large  deposits,  and  is  worked  for 
the  manufacture  of  iron;  .the  same  is  true  of  limonite.  Hematite 
is,  when  a  compact  rock,  hard  and  tough,  and  it  is  difficult  to 
redv.ce  it  to  such  a  degree  of  fineness  as  will  be  suitable  for  a 


128  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

pigment;  the  deposits  of  this  ore  which  are  softer  and  less  com- 
pact are  almost  always  mixed  with  limonite.  The  latter  is 
more  easily  worked  than  the  former  and  is  also  more  abundant. 
The  great  supplies  of  iron-oxide  paints  are  mixtures  of  these, 
and  are  found  in  deposits  where  the  ore  is  in  granular  or  earthy 
form,  usually  mixed  with  more  or  less  clay;  sometimes  the  clay 
amounts  to  two-thirds  the  weight  of  the  whole,  not  uncommonly 
one-half.  Such  a  material  is  easily  reduced  to  a  powder;  it 
is  roasted  in  furnaces  to  drive  off  the  moisture  and  to  develop 
a  color,  then  ground  dry.  The  author  once  operated  one  of 
these  mines;  though  it  was  of  exceptional  character,  a  short 
description  of  the  work  may  be  of  interest. 

Iron  Oxides. — The  ore  was  ferrous  carbonate,  which  had 
been  brought  to  the  surface  by  chalybeate  springs  and  deposited 
In  beds  which  were  overlaid  by  a  deposit  of  peat,  the  reducing 
.action  of  which  preserved  the  ferrous  carbonate  from  oxidation. 
It  was  consequently  a  natural  chemical  precipitate  and  of  extreme 
fineness  as  well  as  purity.  When  this  carbonate  of  iron,  which 
was  nearly  white  in  color,  was  exposed  to  the  air  it  was  rapidly 
oxidized  into  the  ferric  compound;  it  was  put  while  still  moist 
into  a  roasting-furnace,  where  it  was  heated  in  contact  with  air 
and  the  carbonic  acid  driven  off;  the  residue  being,  of  course, 
ferric  oxide.  By  varying  the  heat  and  the  amount  of  air  different 
colors  were  obtained,  from  a  fine  yellowish  red  to  a  dark  purple, 
the  latter  being  the  pigment  known  as  crocus.  The  deep,  strong 
red  of  Indian  red  was  to  be  seen  and  the  dull  brown  of  ordinary 
oxide  paint.  These  colors  were  all  to  be  seen  in  the  same  charge, 
some  lumps  being  of  one  color  and  some  another;  the  whole 
was  run  through  a  mill,  not  to  really  grind  it,  for  it  was  too  fine 
for  that,  but  to  crush  the  agglutinated  lumps,  and  it  came  out  a 
mixture  of  tolerably  uniform  color,  whose  homogeneous  appear- 
ance never  would  suggest  the  fact,  so  obvious  to  the  operator, 
that  it  was  composed  of  oxides  of  many  different  degrees  of 
hydration  and  perhaps  of  oxidation.  The  lesson  to  be  learned 
is  that  it  is  impossible  to  tell  from  the  looks  of  such  a  paint  what 
it  is  made  of,  and  that  it  is  not  impossible  for  a  paint  containing 


OIL  PAINTS  AND   PAINTS  IN  JAPAN.  129 

a  large  percentage  of  iron  oxides  to  have  other  and  deleterious 
ingredients,  since  the  strong  and  dominating  quality  of  the  oxide 
may  overshadow  and  conceal  everything  else.  This  is  without 
doubt  a  considerable  reason  for  the  difference  of  opinion,  about 
the  value  of  oxide  paints,  which  exists.  The  greater  part  of 
these  paints  in  this  country  is  used  for  painting  freight  cars; 
not  a  little  of  the  finer  qualities,  such  as  those  oxides  known 
as  Indian  and  Tuscan  reds,  for  house-painting  and  passenger- 
cars.  Quite  a  large  amount  is  also  used  on  steel  bridges,  chiefly 
in  the  Western  States,  but  its  use  for  this  purpose  is  less  than 
formerly. 

A  large  amount  of  the  better  grades  of  iron  oxides  for  paint 
is  imported  from  England  and  Germany.  These  are  made, 
not  from  minerals,  but  as  by-products  in  chemical  work,  one  of 
the  most  common  being  the  oxide  left  from  the  distillation  of 
sulphate  of  iron  in  making  fuming  sulphuric  acid.  The  cheapest 
way  to  dispose  of  this  is  to  mix  it  with  powdered  chalk,  or  with 
milk  of  lime,  to  absorb  the  sulphuric  acid  remaining  in  it,  which 
is  thus  converted  into  sulphate  of  lime.  The  pigment  known  as 
Venetian  red  is  made  in  this  way  and  contains  a  large  percentage 
of  sulphate  of  lime.  Reds  may  also  be  made  by  washing  and 
roasting  these  residues,  and  some  of  these  are  of  excellent  quality. 
No  colors  are  more  permanent  than  some  of  these  pure  oxides. 
They  have  lasted  for  thousands  of  years  and  there  is  no  reason 
•why  they  should  ever  change,  except  when  they  are  subjected 
to  somewhat  unusual  chemical  action.  Such  a  statement  does 
not,  however,  apply  to  the  impure  oxides  and  especially  it  does 
not  apply  to  the  impure  hydrated  oxide.  It  does  apply  to  the 
pure  anhydrous  and  sometimes  to  the  partially  hydrated  oxide 
when  used  as  a  paint  on  wood  or  some  neutral  base,  and  pro- 
tected either  by  its  situation  or  by  oil  and  varnish  from  access 
of  corrosive  gases  or  liquids.  Under  such  conditions,  as,  for 
instance,  on  the  walls  of  houses  at  Pompeii,  it  seems  absolutely 
permanent,  keeping  its  brilliant  color;  but  although  it  is  a  native 
mineral  and  it  is  evident  from  the  grea':  quantities  which  are 
found  that  it  is  a  compound  of  great  stability,  it  should  not  be 


130  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

assumed  to  be  absolutely  the  most  stable  compound  of  iron, 
incapable  on  that  account  of  change,  as  we  may  think  is  the 
case  with  barytes,  for  instance. 

Iron  Oxides  not  Absolutely  Permanent. — So  accurate  and 
conservative  an  authority  as  Watt's  Dictionary  of  Chemistry 
says,  speaking  not  of  the  comparatively  unstable  hydrate,  but  of 
the  anhydrous  sesquioxide,  that  "even  at  ordinary  temperatures 
it  frequently  acts  as  an  oxidizing  agent  in  contact  with  organic 
matter,  and  is  thereby  reduced  to  magnetic  oxide,  or  even  to 
ferrous  oxide,  and  then,  by  taking  up  carbonic  acid,  converted 
into  spathic  iron;  the  reduced  oxide,  if  in  contact  with  moisture, 
is  frequently  also  reconverted  into  ferric  hydrate  by  atmospheric 
oxidation.  The  oxide  is  also  sometimes  further  reduced  by  the 
action  of  sulphydric  acid  and  converted  into  pyrites." 

The  same  authority  also  says  of  the  hydrated  sesquioxide 
that  it  "  easily  gives  up  part  of  its  oxygen  to  oxidable  bodies 
and  is  easily  reduced  by  sulphurous  acid,  etc.  In  contact  with 
putrefying  organic  bodies,  out  of  contact  with  air,  it  forms  ferroso- 
ferric  compounds,  or  ferrous  carbonate,  but  if  the  air  has  access 
to  it,  it  quickly  recovers  the  oxygen  which  it  has  given  up,  and 
can  then  again  exert  an  oxidizing  action,  thus  acting  as  a  carrier 
of  oxygen  from  the  air  to  the  organic  body ;  hence  it  accelerates 
the  oxidation  of  woody  fibre  in  the  soil." 

It  is  evident  from  the  foregoing  that,  although,  as  has  been 
said,  under  favorable  conditions  some  of  these  oxides  are  among 
the  most  permanent  of  paints,  their  value  depends  on  the  con- 
ditions under  which  they  are  used.  It  is  also  not  to  be  forgotten 
that  when  we  speak  of  permanence  in  a  paint  we,  perhaps  uncon- 
sciously, assume  the  standard  to  be  the  paintings  on  canvas  or 
the  fresco  painting  on  the  interior  walls  of  churches  and  the  like, 
in  all  which  cases  the  paint  has  been  most  carefully  preserved 
and  under  favorable  conditions. 

The  relative  values  of  paints  exposed  to  the  weather  might 
be  quite  different;  in  fact,  such  is  the  universal  experience. 

There  is,  however,  no  reasonable  doubt  that  some  of  the 
iron  oxides  are  valuable  paints.  Some  of  them  are  prepared 


OIL  PAINTS  AND   PAINTS  IN  JAPAN.  131 

from  deposits  of  iron  oxide  mixed  with  clay,  what  might  be 
called  an  iron-bearing  clay  if  we  remember  that  the  iron  is  prob- 
ably present,  not  in  chemical  combination  with  the  clay,  but  as 
intermixed  oxide;  in  these  deposits  the  iron  is  in  a  finely  com- 
minuted condition,  and  these  ores  are  easily  worked  and  easily 
ground,  and  the  resulting  pigment  is  much  less  liable  to  rapid 
settling  out  of  the  oil  or  other  vehicle  than  is  the  heavier  pure 
oxide.  It  is  possible  that  some  of  these  clays  may  be  so  roasted 
as  to  become,  like  brick-dust,  incapable  of  uniting  with  water; 
but  if  not,  they  obviously  are  a  source  of  weakness,  and  in  all 
cases  are  to  be  regarded  with  a  reasonable  amount  of  suspicion. 
There  is,  indeed,  reason  for  suspicion  of  cheap  materials  of  every 
sort,  not  because  cheapness  is  an  objection,  for,  of  course,  it 
is  not  so,  but  in  fact  a  merit,  but  because  it  is  apt  to  blind  the 
eyes  of  the  purchaser  to  such  defects  as  the  material  may  really 
have. 

Iron  oxides  are  also  important  constituents  of  some  of  the 
brown  pigments,  the  most  important  of  which  is  the  earthy 
material  called  sienna,  from  the  Italian  locality  whence  it  is 
obtained.  This  is  of  a  beautiful  red-brown,  and  is  the  pigment 
used  to  make  stains  to  match  mahogany.  Umber  is  a  much 
darker  earth;  both  are  still  further  darkened  by  roasting,  when 
they  are  known  as  burnt  sienna  and  burnt  umber.  Both  are 
said  to  contain  some  oxide  of  manganese,  and  umber  contains 
enough  to  enable  it  to  impart  a  decided  drying  quality  to  oil. 

Bone-  and  Ivory-black. — The  black  pigments  are  various 
forms  of  carbon.  Bone-black  or  ivory-black,  lampblack,  and 
graphite  are  the  principal  sorts.  Bone-black  is  made  by  calcin- 
ing bones  without  access  of  air;  the  organic  matter  contained 
is  decomposed  and  the  oxygen  and  hydrogen  are  mostly  driven 
off,  the  carbon  being  left  with  the  phosphate  and  carbonate  of 
lime  of  the  bone.  Ivory-black  is  made  in  the  same  way  from 
ivory  chips;  but  probably  most  of  the  ivory-black  now  sold  is 
a  fine  grade  of  bone-black.  This  contains  about  10  or  12  per 
cent,  of  carbon,  to  which  it  owes  its  color,  3  or  4  per  cent,  of 
carbonate,  and  the  remainder,  phosphate  of  lime.  It  is  a  brownish 


132  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

black,  the  brown  color  being  partly,  at  least,  due  to  organic  com- 
pounds formed  during  the  roasting,  which  were  too  stable  to 
be  driven  off  at  the  temperature.  These  may  be,  to  a  considerable 
degree,  dissolved  out  by  a  solution  of  caustic  soda,  and  the  better 
grades  are  so  treated.  These  are  of'  a  very  rich  and  velvety 
color. 

Lampblack. — Lampblack  is  made  by  burning  oil  with  an 
insufficient  supply  of  air,  or  rather  by  thrusting  into  the  flame 
a  large  piece  of  cold  porcelain  or  something  of1  the  sort,  which 
so  cools  down  the  flame  as  to  prevent  perfect  combustion,  and 
the  carbon  is  deposited  on  the  cold  surface.  Similar  blacks  are 
made  from  gas-flames,  but  the  details  of  these, processes  are  not 
generally  known,  and  the  variety  of  products  is  surprisingly  large. 
Lampblack  is  always  a  bulky  substance;  of  some  of  the  finer 
sorts  only  4  or  5  pounds  can  be  packed  into  a  barrel,  while  of 
some  of  the  coarser  kinds  20  or  30  pounds  may  occupy  the  same 
space.  It  is  sometimes  adulterated  with  bone-black,  but  this 
makes  it  much  heavier.  The  texture  of  lampblack  is  incon- 
ceivably fine;  mixed  with  oil  in  any  considerable  quantity  it 
greatly  retards  its  drying,  which  may  be  due  partly  to  its  obstruct- 
ing mechanically  the  penetration  of  oxygen,  and  is  certainly 
partly  due  to  the  action  of  oily  matters  always  found  in  it.  It 
is  no  doubt  due  to  these  that  we  find  a  surface  which  has  been 
painted  with  lampblack  retards  the  drying  of  any  paint  applied 
over  it.  Bone-black  is  also  a  non-drier,  but  in  a  less  marked 
degree.  A  very  small  proportion  of  lampblack  is  used  to  affect 
the  color  of  other  paints;  liberally  mixed  with  driers  it  is  used 
alone,  especially  for  signs  and  the  like;  it  is  mixed  with  red  lead 
to  retard  the  setting  of  the  latter  and  to  get  rid  of  its  glaring 
color. 

Graphite  is  a  mineral,  a  crystallized  form  of  carbon,  not  used 
in  common  paints,  but  only  as  a  preservative  against  rust  on  iron. 
Its  use  for  that  purpose  will  be  discussed  later. 

Grinding. — All  these  pigments  may  be  made  into  paints  by 
grinding  them  with  linseed- oil.  There  are  two  ways  of  doing 
this:  in  one  case  we  mix  the  pigment  to  a  paste  with  oil  in  a  mill 


OIL   PAINTS  AND   PAINTS  IN  JAPAN.  133 

especially  designed  for  the  purpose,  and  this  "paste  color,"  as  it  is 
called,  is  thinned  with  rnore  oil,  with  more  or  less  driers  and  tur- 
pentine; in  the  other,  we  put  the  oil  and  dry  pigment  into  a 
" mixer,"  usually  a  vertical  cylindrical  vessel  whose  height  is  Igss 
than_jts_diameter  and  which  is  provided  with  some  sort  of  stirring 
apparatus,  the  simplest  being  a  vertical  revolving  shaft  with 
blades  extending  radially;  after  being  thoroughly  mixed  the  oil 
and  pigment  are  run  through  a  burr-stone  mill  to  make  a  homo- 
geneous mixture.  Sometimes  it  is  necessary  to  put  it  through 
the  mill  a  second  time  or  even  a  third,  when  it  is  put  into  suitable 
packages  for  shipment.  It  is  not  unusual  to  have  some  turpentine 
in  the  mixture;  one  effect  is  to  hurry  the  drying,  because  there  is 
less  oil  to  'dry,  and  because  the  turpentine  itself  acts  to  some 
extent  as  a  carrier  of  oxygen;  another  result  is  that  the  film  con- 
tains a  larger  proportion  of  solid  pigment  than  it  would  otherwise 
have. 

Value  of  the  Pigment.  —  The  effect  of  a  pigment,  aside 
from  its  color  and  any  chemical  action  it  may  exert,  is  threefold. 
Oil  dries  to  a  more  or  less  porous  film;  and  even  a  film  of  var- 
nish is  not  entirely  without  porosity.  The  particles  of  pigment 
stop  up  some  of  these  pores;  this  makes  the  coating  more  imper- 
vious and  consequently  better.  An  oil-film  when  dry  is  a  tough 
but  rather  soft  substance,  easily  scratched  off;  but  the  pigment 
is  a  hard  substance  and  imparts  hardness  and  capacity  for 
resisting  abrasion  to  the  film.  It  is  obvious  that  if  we  mix  a  solid 
powder  with  oil,  the  mixture  will  be  of  a  much  thicker  consistency 
than  oil  alone,  just  as  mud  is  thicker  than  water;  hence  we  can 
spread  a  much  thicker  film  of  such  a  mixture  over  a  surface  than 
we  can  of  oil  alone,  and  this  results  in  having  a  thicker  film,  which 
in  itself  is  desirable.  So  the  film  of  paint  is  less  porous,  harder, 
and  thicker  than  an  oil-film.  If  the  oil  used  be  boiled  oil,  the 
paint  may  be  nothing  but  pigment  and  oil;  though,  as  has  been 
said,  turpentine  is  sometimes  a  good  addition.  But  if  it  be  raw 
oil,  such  a  mixture  will  require  a  week  before  it  seems  to  begin 
to  dry,  and  this  prevents  the  use  of  raw-oil  paints  for  most  pur- 
poses, unless  we  add  to  the  mixture  an  amount  of  drier  sufficient 


134  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

to  make  it  dry  to  the  touch  in  a  day  or  thereabouts.  It  is  a  very 
common  practice  to  add  to  the  oil  more  or  less  oleo-resinous 
varnish,  the  object  being  to  make  a  glossy  paint  and  one  some- 
what harder.  It  is  much  to  be  regretted  that  it  has  become 
common  to  use  for  this  purpose  a  cheap  rosin  varnish,  which  is 
an  injury  to  a  good  oil  paint  in  every  way.  Such  a  paint  does 
not  dry  properly,  and  the  film  will  soften  and  blister  if  exposed 
to  heat;  if  very  much  varnish  is  used  it  will  make  the  film  crack; 
it  is  the  cause  of  most  of  the  cracked  paint  we  see.  But  if  a  good 
varnish  made  of  hard  resins  is  used,  the  effect  will  be  exactly  the 
opposite.  The  trouble  is  that  any  varnish  which  ought  to  be 
used  materially  increases  the  cost  of  the  paint,  and  the  maker, 
who  finds  it  difficult  enough  to  get  a  price  which  will  enable  him 
to  use  pure  oil,  uses  a  varnish  which  costs  less  than  the  oil.  Such 
a  varnish  must  be  pale  in  color,  or  it  will  affect  the  color  of  the 
paint,  and  can  be  made  only  of  common  rosin. 

The  adulterants  of  oil  are  legion.  The  cheapest  are  made  of 
mineral  oil;  these  are  of  little  or  no  value.  It  should  be  said 
that,  as  compared  with  pure  linseed-oil,  nothing  which  can  be 
added  to  it  increases  its  value  except  a  good  varnish;  but  some 
of  these  things  have  some  power  to  form  a  film  and  in  that  sense 
may  be  said  to  have  value.  Probably  the  best  is  fish-oil,  which 
easily  combines  with  driers,  and  if  mixed  in  not  too  great  propor- 
tion with  linseed- oil  forms  a  film  which  dries  after  a  fashion, 
though  slowly,  and  has  fairly  good  weather-resisting  qualities.  A 
mixture  containing  twenty  per  cent,  of  boiled  fish-oil  is  believed 
by  some  good  paint -manufacturers  to  be  superior  to  linseed-oil 
alone  for  a  roof -paint,  but  this  is  doubtful. 

COACH-COLORS. 

For  painting  carriages  and  coaches  oil  paints  are  too  soft 
and  cannot  be  made  to  take  a  sufficiently  smooth  surface.  It  is 
necessary  to  have  a  paint  which  will  be  hard  and  which  can  be 
rubbed  down  with  pumice-stone  until  all  irregularities  of  the 
surface  disappear,  and  an  oil  paint  will  never  get  hard  enough 
for  this.  The  pigment  is,  therefore,  ground  in  varnish,  and  as 


OIL  PAINTS  AND  PAINTS  IN  JAPAN.  135 

no  ordinary  varnish  is  quick  enough  in  drying,  a  special  medium, 
called  grin  ding-japan,  has  been  concocted  for  this  purpose.  This 
is  essentially  an  oleo-resinous  varnish  charged  with  lead  and 
manganese  to  the  highest  degree,  and  it  will  not  only  dry  hard 
itself  in  an  extremely  short  time,  but  so  effective  is  it  as  a  drier  that 
paints  ground  to  a  paste  in  this  vehicle  and  thinned  just  before 
use  with  a  suitable  mixture  of  oil  and  turpentine  will  dry  in  a  few 
hours  to  a  perfectly  hard  surface,  ready  for  the  next  operation. 

Grinding- japan. — The  exact  composition  of  these  grinding- 
japans  is  kept  secret  by  the  makers,  but  the  best  of  them  have 
the  best  quality  of  shellac  for  the  resinous  ingredient,  as  has 
been  stated  in  a  previous  chapter,  and  the  real  secret  is  in  the 
purchase  of  the  best  materials  and  the  use  of  a  sufficient  quantity 
of  good  shellac.  This,  of  course,  makes  the  cost  increase,  but  it  is 
in  the  end  economical,  because  coach-colors  are  sold  by  the  pound 
instead  of  the  gallon,  and  for  rather  high  prices,  as  they  must  be 
because  of  the  labor  expended  on  them,  and  on  account  of  the 
chemical  activity  or  potency  of  the  vehicle  in  which  they  are 
ground  they  are  more  liable  than  most  paints  to  undergo  spon- 
taneous changes  inside  the  can  before  being  opened ;  losses  of  this 
sort,  which  fall  on  the  manufacturer,  are  much  less  if  the  japan 
is  of  the  best  quality.  The  best  is  actually  and  literally  the  cheap- 
est. The  carriage -painter  requires  paints  of  excellent  quality  and 
expects  to  pay  good  prices  for  them,  consequently  pigments  are 
used  which  are  altogether  too  expensive  for  oil  paints;  no  pig- 
ments used  by  artists  are  too  expensive  for  the  best  of  this  work. 

Water-cooled  Mills. — These  paints  cannot  be  ground  in  an 
ordinary  mill,  because  the  friction  develops  heat  and  heat  starts 
up  the  chemical  activity  of  the  japan,  with  the  result  that  the 
color  and  consistency  of  the  product  change;  so  they  are  ground 
in  a  water-cooled  mill.  In  such  a  mill  the  stones  are  cemented  into 
iron  shells,  just  large  enough  in  diameter  to  receive  the  stone, 
which,  however,  does  not  fill  the  cavity  to  the  bottom;  its  edge  is 
cemented  to  the  interior  of  the  iron  shell,  and  a  flat  space  remains 
back  of  the  stone  between  it  and  the  iron.  Through  this  space 
a  stream  of  cold  water  constantly  flows,  and  thus  the  stone  is 


136  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

always  prevented  from  heating.  Both  upper  and  lower  stones 
are  thus  water-cooled  and  the  proper  operation  of  these  mills 
calls  for  the  superintendence  of  a  specially  trained  foreman,  who. 
receives  high  wages,  and  is  commonly  ranked  next  to  the  superin- 
tendent of  the  works.  The  colors  as  they  come  from  the  mill 
should  be  constantly  watched  and  tested  against  standard  sam- 
ples, not  only  for  fineness,  but  especially  for  color.  The  operator 
has  a  slip  of  plain  glass,  on  which  with  a  palette-knife  he  smears  a 
bit  of  paint ;  in  contact  with  it  he  then  lays  on  a  bit  of  the  standard ; 
turning  the  glass  over  and  looking  at  the  paint  through  the  glass, 
the  slightest  difference  is  immediately  noticeable.  For  the  benefit 
of  those  not  familiar  with  these  operations,  it  may  be  said  that 
the  ordinary  burr-stone  mill,  such  as  is  used  for  grinding  all  sorts 
of  substances — for  such  mills  are  used  on  most  diverse  materials 
and  will  economically  grind  a  larger  number  of  substances  than 
all  other  kinds  of  pulverizing  machines  combined — consists  of 
two  flat  circular  stones,  the  upper  of  which  is  fixed  in  a  rigid 
frame,  and  has  an  opening  in  the  centre,  called  the  eye  of  the 
stone,  into  which  is  dropped  the  material  to  be  ground;  the  lower 
stone,  which  has  no  eye,  is  supported  somewhat  loosely  on  the 
upper  end  of  a  shaft,  in  such  a  way  that  when  the  shaft  is  made 
to  revolve  the  stone  revolves,  but  it  is  loose  enough  so  that  when 
pressed  against  the  lower  side  of  the  upper  stone  it  may  adjust 
itself  to  that,  although  the  plane  of  their  junction  may  not  be  at 
right  angles  to  the  axis  of  rotation ;  in  which  case  the  lower  stone 
will  wobble  as  it  revolves.  The  fineness  of  grinding  is  determined 
in  part  by  the  closeness  with  which  the  stones  are  pressed  together. 
In  the  best  form  of  water-cooled  mill  this  construction  is  con- 
siderably modified.  The  lower  stone,  in  its  metal  shell,  is  screwed 
firmly  on  the  top  at  the  shaft,  like  a  face-plate  on  a  lathe,  so  that 
it  cannot  vary  its  position;  the  upper  stone,  instead  of  being 
fixed  to  a  rigid  frame,  is  held  in  a  frame  provided  with  a  universal 
motion,  essentially  like  the  gimbals  which  support  a  ship's  compass, 
and  this  whole  frame  may  be  drawn  down  by  a  tension  screw, 
so  as  to  make  the  upper  stone  fit  itself  to  the  position  of  the  lower 
one.  A  little  consideration  will  show  that  in  the  common  form 


OIL  PAINTS  AND  PAINTS  IN  JAPAN.  137 

of  mill,  having  a  loose  lower  stone,  when  the  stone  is  in  rapid 
motion  it  will  tend,  by  centrifugal  force,  to  take  a  position  at  right 
angles  to  the  axis  of  rotation,  and  as  this  is  not  permitted  by  the 
rigidity  of  the  other  stone,  it  will  press  against  the  latter  on  one 
side  and  be  free  from  it  on  the  other;  which  is  a  fault,  because 
the  two  stones  should  be  pressed  together  in  all  parts  equally.  This 
defect  is  obviated  in  the  newer  form  of  mill,  because  the  lower 
stone  revolves  on  a  rigid  bearing,  and  though  it  may  not  be  dressed 
truly  in  a  horizontal  plane,  the  centrifugal  force  can  produce  no 
effect  on  its  position;  the  upper  stone,  which  is  pressed  against  it, 
has  no  rotary  motion  and  is,  by  the  universal  joint  in  which  it 
swings,  pressed  uniformly  all  the  time.  It  was  for  a  long  time 
believed,  and  by  many  experienced  but  not  well-informed  people 
is  still  believed,  that  colors  can  be  ground  to  an  extreme  degree 
of  fineness  only  on  a  stone  slab  with  a  muller,  as  described  by 
Cennini,  in  a  passage  already  quoted,  because  with  such  a  rudi- 
mentary apparatus  the  intelligence  and  watchful  patience-  of  the 
operator  secures  a  uniform  grinding  and  the  slowness  of  the 
operation  prevents  heating;  at  least,  it  is  the  operator  and  not  the 
paint  that  gets  warm;  but  in  a  water-cooled  mill  of  the  improved 
design,  which  has  been  described,  these  good  results  are  auto- 
matically secured  and  the  paint  is  besides  protected  from  the 
action  of  the  air  and  the  dust  during  grinding,  and  by  putting  it 
through  the  mill  as  many  times  as  may  be  desired  it  may  be 
ground  to  any  degree  of  fineness.  Artist's  colors  of  unequalled 
excellence  are  now  made  in  this  way,  and  it  is  obvious  that  colors 
can  be  ground  in  a  volatile  medium  like  turpentine  or  varnish 
only  with  such  a  machine.  These  mills  have  been  in  use  about 
twenty  years,  but  are  still  unknown  to  many.  Water-cooled 
mills  of  the  older  pattern  are  of  much  earlier  date. 

Few  of  my  readers  know  where  to  look  for  the  oldest  paint-mill 
in  America.  It  was  very  different  from  those  now  in  use ;  it  con- 
sisted of  a  large  flat  rectangular  stone,  hollowed  out  to  form  a 
stone  trough  capable  of  holding  seventy-five  or  a  hundred  gallons 
of  paint ;  the  materials  for  which,  having  been  put  in  the  trough, 
were  mixed  and  ground  together  by  a  stone  ball,  about  two  feet 


138  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

in  diameter,  which  was  rolled  from  end  to  end  of  this  receptacle, 
and  served  both  to  mix  and  grind  the  contents. 


This  mill  is  in  Boston  Mfass.  As  you  walk  down  Hanover 
Street  from  Washington  Street,  keeping  on  the  south  side  of 
Hanover,  just  before  reaching  Blackstone  Street,  you  may  notice 
a  narrow  lane  called  Marshall  Street,  turning  off  to  the  right. 
Down  this  alley  about  fifty  feet  there  is  a  little  open  triangular 
space;  when  you  reach  it  turn  around,  and  in  the  foundation 
of  the  building  in  front  of  you  (which  faces  on  Hanover)  you  will 
see  the  "Boston  Stone,"  as  represented  in  the  accompanying 
illustration.  This  is  the  old  paint-mill  which  was  imported  from 
England  about  the  year  1700  by  a  painter  who  had  a  little  shop 
in  the  old  wooden  house  that  then  occupied  this  site.  It  is,  there- 
fore, more  than  two  hundred  years  old. 

Following  the  custom  of  the  times,  he  placed  on  the  Hanover 
Street  front  of  his  home  the  English  coat  of  arms  carved  in  wood, 
with  his  initials  and  the  date,  1701,  upon  it,  from  which  his  dwelling 
came  to  be  known  as  the  "Painter's  Arms."  When  the  old  frame 
house  was  removed  in  1835,  the  "Painter's  Arms"  were  taken 
down  and  replaced  on  the  new  building. 

At  the  same  time,  the  Boston  Stone,  which  had  also  been  tem- 
porarily removed,  was  put  back  in  the  position  it  now  occupies. 
The  round  stone  above,  which  is  about  two  feet  in  diameter, 
was  the  grinder  or  "muller,"  and  was  rolled  back  and  forth  in 
the  trough  hollowed  out  in  one  side  of  the  larger  stone  under- 
neath and  thus  ground  the  paint.  The  grinder  was  once  lost 


OIL  PAINTS  AND   PAINTS  IN  JAPAN.  139 

for  a  time,  and  was  discovered  in  digging  the  foundation  for  the 
present  building;  the  trough-stone  was  found  in  the  yard  of  the 
house  when  the  place  was  bought  from  the  painter,  and  as  the 
stone  was  of  no  use  there,  it  was  removed  to  the  corner  of  the 
house  to  protect  the  building  from  injury  by  carts.  For  some 
time  after  it  had  been  placed  in  this  position  it  was  utilized  by 
surveyors  as  a  starting-point  from  which  to  run  their  lines.  The 
original  stone,  the  capacity  of  which  is  said  to  have  been  nearly 
two  barrelfuls  of  paint,  was  finally  split  into  four  pieces,  and  it 
is  one  of  these  fragments  that  now  rests  under  the  grinder  with  the 
inscription  "Boston  Stone  1737"  cut  in  it.  The  way  in  which 
it  came  to  be  called  the  Boston  Stone  is  thus  described  by  a  local 
antiquarian : 

"When  I  was  a  boy,"  said  Dr.  Elliott,  "in  passing  the  build- 
ing, I  saw  a  lad  named  Joe  Whiting,  whose  father  occupied  the 
shop,  writing  on  the  stone  these  words :  '  Boston  Stone,  Marshall 
Lane.5  After  I  became  a  man,  I  asked  Mr.  Whiting  who  set 
the  boy  at  work  on  the  stone.  He  said :  '  Marshall  Lane  at  that 
time  not  being  named,  it  was  difficult  to  designate  his  place  of 
business.  A  Scotchman  who  opened  a  shop  for  the  sale  of  ale 
and  cheese,  directly  opposite,  made  a  complaint  of  the  difficulty. 
He  said  in  London  there  was  a  large  stone  at  a  certain  corner 
marked  London  Stone,  which  served  as  a  direction  to  all  places 
near  it,  and  if  I  would  let  Joe  write  the  words  Boston  Stone  on 
this,  people  would  notice  it  and  it  would  set  them  guessing  what 
it  meant,  and  would  become  a  good  landmark. ' ' 

That  the  Scotchman  was  right,  in  his  belief  is  proved  by  the 
fact  that  for  generations  past  the  dull  red,  weather-stained  stone, 
with  the  deeply  cut,  white  lettering,  has  been  one  of  the  land- 
marks of  the  North  End,  so  well  known  that  we  find  it  in  Whit- 
tier's  stirring  appeal : 

"Woe  to  thee,  when  men  shall  search 
Vainly  for  the  Old  South  Church; 
When,  from  Neck  to  Boston  Stone, 
All  thy  pride  of  place  is  gone; 
When  from  Bay  and  railroad  car, 
Stretched  before  them  wide  and  far, 
Men  shall  only  see  a  great 
Wilderness  of  brick  and  slate!" 


CHAPTER   XIII. 

VARNISH  OR  ENAMEL  PAINTS. 

ALL  oleo-resinous  varnishes  are  more  or  less  dark  in  color 
The  very  pale  ones  are  yellow;  the  medium  ones  are  brownish 
yellow;  the  dark  ones  are  yellowish  brown.  If,  therefore,  we 
apply  a  coat  of  varnish  over  a  painted  surface,  the  color  of  the 
latter  will  be  changed ;  and  in  order  to  avoid  this,  the  painter  may 
mix  some  of  his  pigment  in  the  varnish,  thus  bringing  the  pig- 
ment to  the  surface  and  displaying  its  color,  with  less,  but  not 
entirely  without,  influence  from  the  color  of  the  varnish.  Of 
course,  if  the  paint  is  dark  in  color,  the  color  of  the  varnish  is  of 
no  account,  but  to  make  a  white  enamel  paint  taxes  the  resources 
of  the  most  skilful  varnish-maker.  There  are  indeed  varnishes 
which  are  nearly  free  from  color,  such  as  bleached  shellac;  but 
shellac  is  an  acid  resin,  and  if  we  mix  white  lead  or  white  zinc  with 
it,  a  chemical  action  is  at  once  set  up  and  a  doughy  mass  not  in 
the  least  resembling  paint  is  formed.  There  are  some  spirit 
varnishes  which  may  be  mixed  immediately  before  using  with 
these  pigments,  but  they  lack  durability. 

Damar  Enamel. — The  one  most  generally  liked  on  account 
of  its  free  working  quality,  its  color,  and  its  moderate  price  is 
damar,  but  this  has  not  a  very  good  lustre;  it  is,  and  always 
remains,  soft,  or  at  least  does  not  approach  an  oleo-resinous 
varnish  in  hardness,  and  it  soon  loses  whatever  gloss  it  had 
in  the  beginning,  and  if  exposed  to  the  weather  it  is  almost  imme- 
diately destroyed.  It  is  a  good  deal  used  in  making  white  enamel 
for  iron  beds  and  the  like,  and  is  hardened  by  baking.  This 
also  greatly  improves  its  lustre  and  its  durability,  and,  as  it  is 
not  to  be  exposed  to  the  weather  or  even  to  the  sun,  it  is  fairly 

140 


VARNISH  OR  ENAMEL  PAINTS.  141 

satisfactory  for  this  purpose.  White  is  the  color  of  sunlight,  and 
a  surface  of  clean  snow  is  probably  the  whitest  thing  we  ever 
see;  no  pigment  will  £>ear  comparison  with  it.  So  when  we 
talk  of  paints  white  is  a  comparative  term;  some  paints  look 
more  like  white  than  others,  and  the  best  of  them  when  ground 
in  oil  look  decidedly  yellow,  from  the  color  of  the  vehicle,  if  com- 
pared with  the  pigment  either  dry  or  made  into  a  water-color. 
Artists  frequently  use  poppy-oil  or  walnut-oil,  which  are  drying 
oils  (but  less  drying  than  linseed)  because  of  their  pale  color, 
but  the  advantage  is  only  temporary,  because  they  yellow  with 
age  quite  as  much  as  linseed.  Indeed  they  are  much  worse 
because  it  is  necessary,  in  order  to  make  them  dry,  to  load  them 
with  driers  far  beyond  the  need  with  linseed-oil,  and  this,  as  has 
been  explained,  has  a  most  injurious  effect  on  their  permanence. 
All  these  oils  with  age  turn  yellow,  especially  in  the  dark  or  in 
weak  light,  and  may  from  time  to  time  be  bleached  by  exposure 
to  the  direct  sunlight.  A  painted  surface,  as,  for  example,  the 
outside  of  a  house,  continually  exposed  to  the  sun  remains  white. 
Varnish  paints,  however,  do  not  change  in  any  such  marked 
manner;  they  do  not  grow  yellow,  nor  are  they  bleached  by 
sunlight  very  much.  White  lead  or  zinc  ground  in  oil  is  whiter 
than  any  oleo-resinous  varnish  paint,  at  least  after  being  sun- 
bleached,  but  very  white  enamel  paint  may  be  made  if  the  neces- 
sary expense  is  warranted. 

These  enamel  paints  are  certainly  the  highest  achievement 
of  the  paint -maker's  art.  They  are,  like  the  varnishes,  unlimited 
in  variety,  and  may  be  made  of  quality  suitable  for  the  most 
diverse  uses.  If  they  are  to  be  used  on  furniture,  they  will  be 
made  with  a  hard  varnish  and  may  be  rubbed  and  polished  like 
a  varnished  surface;  if  for  interior  woodwork  of  a  house,  a  more 
elastic  varnish  will  be  used,  and  to  stand  exposure  to  the  weather 
the  varnish  must  be  made  especially  for  such  service.  The  maker 
must  know  first  what  pigments  he  will  have  to  supply,  then  he  will 
consider  what  varnishes  he  has  found  suitable  for  use  with  these 
pigments ;  from  a  list  of  these  he  selects  such  as  will  make  a  vehicle 
at  once  elastic  in  a  high  degree  and  hard  to  resist  abrasion,  with 


142  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

toughness  to  act  as  a  binder  and,  especially  if  it  is  to  be  used  on 
metal  or  any  impermeable  material,  extremely  adhesive.  When 
a  suitable  mixture  is  found  and  ground  with  pigments  which  are 
chemically  inert  and  permanent  we  have  a  paint  of  the  highest 
degree  of  excellence.  As  a  matter  of  practice  the  greater  propor- 
tion of  enamel  paints  are  light  in  color  and,  therefore,  have  white 
lead  or  white  zinc  as  a  base,  and  the  varnish  used  must  be  such  as 
will  work  properly  with  these  pigments,  which,  as  they  cannot  be 
called  chemically  inert,  are  somewhat  difficult  to  fit  with  an  other- 
wise suitable  vehicle.  The  kauri  varnishes  seem  to  work  better 
than  any  others,  perhaps  because  they  are  so  completely  free  from 
•acidity;  those  made  from  the  softer  resins  and  from  some  of  the 
harder  resins  do  not  behave  as  well. 

Defects  of  Enamels. — The  trouble  is  that  the  mixture  becomes 
thick,  and  if  we  thin  it  with  more  varnish  or  turpentine  we,  of 
course,  have  less  than  the  normal  amount  of  pigment  in  it  and  it 
lacks  covering  power ;  moreover,  the  paint  becomes  ropy  with  age 
and  no  amount  of  thinning  will  make  it  spread  freely  and  uniformly. 
I  have  never  seen  enamel  paint  containing  much  white  lead  (and 
zinc,  which  works  better  in  cheap  enamels,  is  quite  as  bad  in  those 
of  better  quality)  which  did  not  deteriorate  somewhat  on  standing 
a  long  time.  This  is  a  serious  obstacle  to  their  general  use,  and 
even  when  fresh  they  do  not  and  can  not  flow  like  an  oil  paint,  nor 
do  they  equal  the  oil  paints  in  covering  power.  This  is  because 
the  varnish  is  much  more  viscid  than  oil  alone,  and  if  we  put  as 
much  pigment  to  a  gallon  of  varnish  as  we  would  do  to  a  gallon  of 
oil,  the  mixture  would  be  too  thick  to  work  properly  under  the 
brush.  The  enamel  paint  is,  therefore,  comparatively  trans- 
parent and  it  requires  a  great  many  coats  to  make  a  substantial 
foundation  of  color.  Hence  it  is  the  common  practice  to  lay  on  a 
foundation  of  oil  paint,  which  has  much  more  covering  body,  until 
we  get  the  desired  color ;  then  finish  with  as  many  coats  of  enamels 
as  may  be  necessary.  This  is  a  violation  of  the  general  rule, 
to  be  hereafter  discussed,  that  the  under-coat  should  always  be 
harder  or  not  less  hard  than  the  outer  one,  and  for  severe  expos- 
ure out  of  doors  it  should  not  be  followed;  but  for  interior  work, 


VARNISH   OR  ENAMEL  PAINTS.  143- 

where  nearly  all  enamel  is  used,  it  is  usually  satisfactory,  and  it 
is  not  only  less  expensive  but  far  less  tedious  than  building  up  a. 
body  of  solid  enamel  paint. 

Enamel  may  be  Thinned  with  Varnish. — When  it  is  necessary, 
as  it  sometimes  is,  to  thin  the  enamel  paint  at  the  time  of  applying 
it,  this  should  never  be  done  with  oil,  and  it  is  not  advisable  to  do 
it  with  turpentine,  but  with  varnish;  and  the  varnish  should  be 
slower-drying  than  the  enamel.  It  would,  of  course,  be  right 
to  use  the  same  varnish  the  enamel  was  made  of,  but  this  is  not 
often  possible,  and  it  is  good  safe  advice  to  use  for  the  purpose  a 
finishing  carriage -varnish,  or  "wearing  body"  varnish  as  it  is. 
often  called,  which  is  at  once  pale  in  color,  elastic,  and  possessed 
of  the  very  finest  working  qualities.  Spar- varnish  is  also  suitable. 
These  varnishes  should,  of  course,  be  from  reliable  makers,  because 
not  a  little  inferior  varnish  is  put  out  under  these  names.  It  is 
extremely  dangerous  (that  is,  to  the  quality  of  the  paint)  to  add 
oil  to  any -enamel  paint,  or  to  a  varnish,  for  that  matter;  there  is 
no  objection,  usually,  to  adding  a  good  varnish  to  oil  or  an  oil  paint, 
for  if  it  does  no  good  it  probably  will  do  no  harm;  but  adding  oil 
to  varnish  is  only  less  reprehensible  than  adding  drier  or  japan  to 
it,  all  of  which  things  are  not  infrequently  done  by  persons  of  a 
sufficient  degree  of  depravity.  Enamels  are  sometimes  made  by- 
grinding  the  pigment  in  oil  to  a  paste  and  then  thinning  this  with 
varnish,  and  fairly  good  enamels  may  be  made  in  this  way;  but  it  is. 
better  to  grind  the  pigment  directly  with  the  varnish,  because  add- 
ing in  even  this  indirect  way  oil  to  the  varnish  slows  down  its  drying 
beyond  all  reason  and  makes  it  necessary  to  use  a  quick-drying 
varnish,  when  we  might  just  as  well  use  all  varnish  and  use  one 
which  would  be  slower  and  much  more  durable  and  have  better 
working  qualities.  On  the  other  hand,  remembering  what  has 
been  said  about  the  necessity  of  using  mixtures  of  different  var- 
nishes to  get  a  compound  of  the  right  character,  we  may  usually 
select  a  varnish  to  grind  the  color  into  a  paste,  which  will  be 
especially  suited  for  grinding,  and  in  which  the  pigment  will  keep 
well,  and  when  the  paint  is  called  for,  some  of  this  paste  may  be 
taken  and  mixed  with  the  varnish  which  is  to  be  used,  the  mixture 


144  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

Tim  through  a  mill  to  insure  the  proper  mixing,  and  it  is  ready  to 
ship.  It  is  generally  a  good  plan  to  have  your  principal  varnishes 
mixed  and  tanked  for  a  month  or  more  before  putting  into  cans, 
because  it  takes  a  long  time  for  the  components  which  have  sensi- 
bly the  same  physical  qualities  to  become  uniformly  mixed,  and 
this  is  an  objection  to  thinning  a  varnish,  even  with  pure  turpen- 
tine, and  a  reason  why  such  a  practice  seems  so  seriously  to  injure 
its  working  qualities ;  if  we  add  the  turpentine  and  mix  it  as  well 
as  we  can  and  then  set  it  away  for  a  month  or  two,  we  shall  find  a 
great  difference.  Any  one  may  illustrate  this  by  making  a  syrup 
•of  sugar  and  water,  and  pour  some  of  this  thick,  ropy  syrup  into  a 
bottle  of  pure  water;  though  perfectly  miscible,  it  will  take  an 
astonishing  amount  of  shaking  before  the  two  liquids  become, 
even  to  the  eye,  completely  mixed.  But  this  does  not  hold  true 
in  case  of  these  enamel  paints,  because  we  run  the  mixture  (which 
we  admit  to  be  an  imperfect  one)  of  paste  color  and  varnish 
through  the  mill,  and  this  mixes  them  in  the  most  perfect  manner ; 
the  mixture  is  much  more  complete  than  would  be  the  case  if  no 
pigment  were  present. 

It  has  already  been  said  that  some  of  these  paints  are  made 
with  damar;  it  has  also,  in  an  earlier  chapter,  been  remarked 
that  damar  varnish  is  often  adulterated  with  rosin,  even  up  to  the 
vanishing-point,  and  these  various  statements  may  be  combined, 
when  they  explain  the  composition  of  some  of  the  most  atrocious 
compounds  known  in  the  whole  paint  business.  It  would  be  a 
waste  of  words,  and  of  the  sort  of  words  which  do  not  look  well 
in  a  book,  to  describe  these  products,  which  are  in  no  small  degree 
responsible  for  the  poor  opinion  of  enamel  paints  held  by  many 
worthy  and  otherwise  intelligent  people.  It  is  not  to  be  denied 
that  varnish  or  enamel  paints  have  their  drawbacks;  as  has  been 
said,  they  do  not  work  as  freely  as  oil  paints,  they  are,  especially 
in  white,  a  little  less  brilliant  in  color,  they  do  not  cover  as  well, 
and  they  do  not  keep  well  in  the  can,  but  they  work  freely  enough 
so  that  a  good  workman  can  do  the  finest  sort  of  work  with  them 
when  they  are  fresh;  their  lustre  more  than  makes  up  for  any 
slight  yellowing  of  the  color,  which  is  at  any  rate  noticeable  in 


VARNISH   OR  ENAMEL  PAINTS  145 

hardly  anything  but  white;  they  have  fair  covering  quality,  and 
the  dark  shades,  which  are  made  with  opaque  pigments,  cover 
perfectly;  some  of  them  appear  to  keep  in  the  can  indefinitely, 
and  even  the  whites,  which  are  the  worst,  will  usually  keep,  espe- 
cially in  a  cool  place,  a  year  or  more,  which  is  longer  than  any 
paint  ever  should  be  kept,  for  it  is  a  general  rule  that  paint  is  best 
when  it  comes  from  the  mill.  Varnishes  are  thought  to  improve 
by  keeping,  but  such  a  thing  has  never  been  supposed  of  paint, 
even  oil  paint,  except  that  white  lead  and  oil  are  supposed  to 
improve  for  a  time. 

Special  Enamels  for  Special  Uses. — Paints  of  this  sort,  like 
varnishes,  should  be  made  for  the  special  uses  to  which  they  are 
to  be  put;  it  is  not  practicable  to  use  one  kind  for  all  sorts 
of  work,  interior  and  exterior,  and  even  out  of  doors  there  are 
many  places  where  a  fine  appearance  is  essential  and  others 
where  this  is  of  less  account  than  extreme  durability.  Dark 
and  dull  colors  are  in  general  more  durable  than  light  and  bril- 
liant ones;  this  is  true  also  of  oil  paints.  If  a  paint  is  to  be  sub- 
ject to  frequent  rubbing,  as  on  a  hand-rail,  or  to  blasts  of  dust, 
as  on  a  railway  car,  it  must  have  hardness  to  resist  abrasion, 
or  it  will  not  answer  at  all;  and  it  may  be  that  the  necessary 
hardness  cannot  be  had  without  making  the  paint  so  inelastic 
that  it  will  in  time  crack  from  the  rapid  and  extreme  changes 
of  temperature  it  must  endure;  but  if  it  is  to  stand  the  weather 
alone,  it  may  be  made  so  tough  that  it  can  never  possibly  crack, 
and,  being  practically  water-proof,  which  an  oil  paint  is  not,  it 
will  resist  decomposition  longer  than  any  other  preservative  coat- 
ing. But  such  a  paint  as  that  would  be  entirely  out  of  place  on 
the  interior  finish  of  a  house,  and  if  applied  to  articles  of  fur- 
niture, it  would  make  a  horrible  mess.  Yet  with  suitable  enamels 
the  most  dainty  articles  of  the  toilet-table  are  painted,  and  all 
the  most  valuable  pictures,  made  in  the  middle  ages  by  the  great 
masters  of  art,  have  come  down  to  us  painted  with  pigments 
.ground  in  just  such  varnish  as  we  are  making  to-day. 


CHAPTER  XIV. 

CHINESE  AND  JAPANESE  LACQUERS. 

THE  Jesuit  missionary  Father  D'Incarville,  who  was  a  cor- 
responding member  of  the  French  Academy  of  Sciences,  wrote 
from  China  a  memoir  on  Chinese  varnish;  this  was,  as  stated 
in  the  text,  a  few  years  after  the  death  of  the  Emperor  Yung- 
ching  or  Yong-toking,  and  in  the  beginning  of  the  reign  of  Keen- 
lung;  that  is,  a  few  years  after  1735.  This  memoir  was  said  by 
Watin  to  be  practically  inaccessible  in  1772;  inaccurate  state- 
ments said  to  be  based  on  it  appear  in  various  encyclopaedias; 
and  as  the  writer  has  been  so  fortunate  as  to  have  secured  a  copy, 
the  following  translation,  which  is  complete  with  the  except  ion 
of  a  few  irrelevant  sentences,  is  now  presented,  as  an  important 
addition  to  our  knowledge  of  the  subject.  The  author  claimed 
no  knowledge  of  varnish  in  general,  but  simply  wrote  out  his 
own  observations.  The  mention  of  tung-oil  is  the  earliest  which 
has  come  to  the  notice  of  the  translator. 

D'INCARVILLE'S  MEMOIR. 

It  is  commonly  known  in  Europe  that  Chinese  varnish  is  not 
a  composition,  but  a  gum  or  resin  which  runs  from  a  tree  which 
the  Chinese  call  Tsichou,  or  varnish-tree. 

This  tree  grows  in  most  of  the  southern  provinces  of  China; 
it  grows  wild  in  the  mountains;  the  trunk  of  the  tree  is  some- 
times a  foot  or  more  in  diameter.  Those  which  are  cultivated 
on  the  plains,  or  on  certain  mountains,  the  Chinese  tap  for  their 
juice  when  they  are  as  large  as  one's  leg;  these  cultivated  trees 

do  not  live  more  than  about  ten  years. 

146 


CHINESE  AND   JAPANESE  LACQUERS.  14? 

Varnish-trees. — The  varnish-tree  is  easily  propagated  from 
slips;  in  the  autumn  they  select  such  branches  as  they  wish  to 
use  for  this  purpose;  they  pack  the  twig  not  too  firmly  with 
earth,  a  few  inches  beyond  the  place  where  it  is  to  be  cut  off,  and 
this  earth  is  formed  into  a  ball  about  the  size  of  one's  head,  and 
wrapped  in  tow  or  linen  cloth  to  keep  it  in  shape;  they  water  it 
occasionally  to  keep  it  moist ;  the  branch  puts  forth  roots,  and  in 
the  spring  it  is  cut  off  above  the  ball  of  earth  and  is  transplantable. 

This  tree  grows  as  well  in  an  open  country  as  in  the  moun- 
tains, and  the  varnish  is  quite  as  good,  provided  that  the  situation 
is  favorable;  if  the  trees  have  not  a  good  exposure  or  are  in  the 
shade,  they  give  more  varnish,  but  not  as  good.  This  tree  requires 
no  other  culture  than  to  have  the  earth  stirred  beneath  it,  and 
to  fertilize  it  with  the  leaves  which  fall  from  the  tree. 

Collection  of  Varnish. — The  varnish  is  collected  in  summer. 
If  it  is  a  cultivated  tree,  the  sap  is  drawn  three  times ;  that  which 
is  taken  first  is  best,  and  the  second  is  better  than  the  third.  If 
the  trees  are  wild,  they  tap  them  but  once  a  year;  or  if  they  do 
it  three  times,  they  then  leave  the  tree  undisturbed  for  three  years. 

To  obtain  the  varnish  they  make,  with  a  knife,  three  cuts 
which  go  through  the  bark  but  do  not  raise  it.  These  three  cuts 
form  a  triangle;  in  the  base  of  this  triangle  they  insert  a  clam- 
shell to  receive  the  liquid  which  runs  out  from  the  other  two  cuts ; 
this  is  the  practice  with  cultivated  trees.  With  wild  ones  they 
.make  a  cut  in  the  tree  with  a  hatchet,  as  they  do  in  Europe  to 
get  turpentine  from  the  pine.  It  is  possible  to  make  twenty 
incisions  in  one  of  these  large  trees;  but  on  the  cultivated  ones 
they  set  not  more  than  four  shells  at  a  time,  and  they  make  new 
cuts  each  time  they  wish  to  get  more  varnish. 

It  sometimes  happens  to  the  great  wild  trees  that  after  having 
made  the  incisions  the  varnish  does  not  run ;  it  is  then  necessary  to 
slightly  moisten  the  cut  surfaces;  for  this  they  provide  themselves 
with  hogs'  bristles,  some  of  which  they  moisten,  if  water  is  not 
at  hand,  with  saliva,  and  put  about  the  place;  which  treatment, 
by  moistening,  opens  the  pores  of  the  tree  and  lets  the  varnish 
escape. 


148  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

When  it  appears  that  one  of  the  wild  trees  is  exhausted,  and 
there  is  no  hope  of  getting  more  from  it,  they  cover  the  top  of 
the  tree  with  a  little  straw,  which  they  set  on  fire,  and  all  the 
remaining  varnish  in  the  tree  is  precipitated  into  the  numerous 
incisions  which  they  have  made  near  the  foot  of  the  tree. 

Those  who  collect  it  go  out  before  daybreak.  In  the  morning 
twilight  they  set  the  shells  in  place;  each  man  can  set  about  a 
hundred.  These  they  leave  about  three  hours,  after  which  they 
collect  the  varnish,  beginning  with  those  first  set.  If  the  shells 
are  left  longer  the  varnish  is  better,  but  less  in  quantity,  because 
the  sun  evaporates  the  aqueous  parts,  and  this  would  cause  a 
loss  to  the  seller. 

The  collector  carries,  hung  to  his  girdle,  a  little  bucket  of  bam- 
boo in  which  he  deposits  the  varnish.  To  do  this  he  moistens 
his  finger  by  passing  it  over  his  tongue,  and  in  wiping  out  the 
shell  the  varnish  does  not  stick  to  his  finger  because  it  is  moist. 
Some  use  a  little  wooden  spatula  which  they  moisten  with  water 
or  with  the  tongue. 

Storage  of  Varnish. — What  each  one  collects  in  his  little 
bucket  he  carries  to  the  dealer,  who  preserves  it  in  casks.  These 
buckets  and  casks  are  carefully  covered  with  a  sheet  of  paper,  as 
confectioners  cover  their  jars  of  preserves  with  a  circular  piece 
of  paper  cut  to  fit  the  top  of  the  jar.  Those  who  collect  the  varnish 
do  not  take  the  trouble  to  cut  out  the  paper  in  this  way,  but  they 
fit  it  over  the  mouth  of  the  vessel,  to  preserve  the  varnish  better, 
and  to  prevent  the  entrance  of  the  least  dust.  Their  paper,  which 
they  call  Moteou-tchi,  is  very  suitable  for  this;  it  is  made  of 
hemp. 

Its  Poisonous  Qualities. — It  is  necessary  to  take  care,  in  cover- 
ing and  opening  the  vessels  which  contain  the  varnish,  not  to 
expose  one's  self  to  the  vapor;  the  face  should  be  turned  to  one 
side;  unless  one  is  careful  there  is  risk  of  getting  an  eruptive 
disease,  such  as  is  caused  by  the  poison-ivy  of  Canada,  except 
that  the  poisoning  by  varnish  is  much  worse;  but  it  is  not  fatal. 
To  lessen  the  burning  sensation  of  these  blisters  they  bathe  them 
with  cold  water,  if  they  have  not  burst ;  but  if  they  have,  they 


CHINESE  AND   JAPANESE  LACQUERS.  149 

rub  them  with  the  yellow  matter  taken  from  the  bodies  of  crabs, 
or,  if  that  is  not  to  be  had,  with  the  flesh  of  shell- fish,  which  by  its 
coolness  gives  much  relief.  Few  of  those  who  work  in  varnish 
are  exempt  from  being  attacked  once  by  this  disease.  It  is  some- 
what singular  that  people  who  are  active  and  highly  colored  are 
more  subject  to  it  than  those  of  a  phlegmatic  temperament. 
Some  of  the  latter  are  never  attacked. 

To  keep  the  varnish  they  set  the  vessels  in  caves  where  it  is 
cool  and  not  too  damp ;  being  well  covered,  they  keep  it  as  long 
as  they  wish. 

The  varnish,  when  it  comes  from  the  tree,  resembles  liquid 
pitch;  exposed  to  the  air  it  takes  on  a  reddish  color,  and  soon 
becomes  black,  but  not  a  brilliant  black  because  of  the  water 
which  it  contains. 

Three  Kinds. — The  Chinese  distinguish  three  sorts  of  varnish : 
the  Nien-tsi,  the  Si-tsi,  and  the  Kouang-tsi.  The  three  words, 
Nien,  Si,  and  Kouang,  are  three  names  of  the  principal  cities 
from  which  they  get  the  three  kinds  of  varnish,  namely,  Nien- 
tcheou-fou,  Si-tcheou-fou,  and  Kouang-tcheou-fou.  Tcheou-fou 
signifies  principal  city,  or  city  of  the  first  class. 

The  Nien-tsi  and  the  Si-tsi  are  two  species  of  varnish  which 
they  employ  to  make  the  black  varnish ;  the  Nien-tsi  is  the  better, 
but  it  is  very  difficult  to  get  it  pure :  the  dealers  mix  Si-tsi  with  it. 

The  province  from  which  they  get  the  Nien-tsi  is  not  very 
extensive,  and  so  there  is  not  enough  of  it  for  all  the  work  done 
in  China.  The  Nien-tsi  is  of  a  more  brilliant  black  than  the 
Si-tsi;  it  costs  at  Pekin  about  a  hundred  sous  for  a  livre  (one 
dollar  a  pound);  the  Si-tsi  is  one-third  as  costly.  The  Kouang- 
tsi  is  of  a  yellowish  color;  it  is  more  pure,  or  contains  less  water, 
than  the  other  kinds. 

Tong-oil. — It  has  another  advantage :  it  is,  that  in  using  it 
they  mix  it  with  about  half  of  Tong-yeou,  which  is  another  varnish, 
or  rather  an  oil  very  common  in  China,  which,  at  the  places 
where  it  is  produced,  costs  only  two  or  three  cents  per  pound.  I 
have  heard  say  that  they  sell  it  at  Paris  under  the  name  of  Chinese 
varnish.  It  resembles  turpentine.  I  have  said  that  they  mix 


150  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

half  of  this  oil  in  the  varnish  called  Kouang-tsi;  that  depends  on 
the  purity  of  the  varnish:  if  it  is  very  pure  they  add  more  than 
half;  then  the  price  is  nearly  that  of  Nien-tsi. 

Drying  by  Evaporation. — It  is  first  necessary  to  remove  from 
it  the  aqueous  part  by  evaporating  it  in  the  sun;  unless  this  is 
done  it  will  never  become  brilliant.  The  Chinese  set  about  it 
in  the  following  manner:  they  have  for  the  purpose  large  flat 
vessels  the  rim  of  which  is  not  more  than  an  inch  or  an  inch  and 
a  half  in  height;  these  are  a  sort  of  basket  of  woven  reeds  or 
osiers,  plastered  with  a  composition  of  earth  or  ashes,  over  which 
is  a  single  layer  of  common  varnish.  They  are  convenient  for 
holding  the  varnish  while  it  evaporates,  and  it  can  be  removed 
from  them  easily. 

If  the  sun  is  warm,  two  or  three  hours  are  enough  to  remove 
the  moisture  from  the  varnish,  which  is  not  more  than  an  inch 
deep  in  the  dish.  While  it  is  evaporating  they  beat  it  with  a 
wooden  stirrer  almost  incessantly,  turning  and  re -turning  it ;  first 
it  forms  white  bubbles,  which  diminish  in  size  little  by  little; 
finally  they  take  on  a  violet  color;  then  the  varnish  is  sufficiently 
evaporated. 

Further  Treatment. — When  from  this  varnish,  which  I  sup- 
pose to  be  Nien-tsi,  to  which  they  have  added  a  fourth  part  of 
Si-tsi,  they  wish  to  make  the  fine  ordinary  varnish  of  China,  after 
having  evaporated  it  about  half  they  add  to  it  about  three-quarters 
of  an  ounce  of  hog's  gall  to  a  pound  of  varnish:  it  is  necessary 
that  this  gall  should  have  been  previously  evaporated  in  the  sun 
until  it  becomes  somewhat  thick;  without  this  hog's  gall  the 
varnish  would  be  lacking  in  body,  it  would  be  too  fluid. 

After  having  stirred  this  gall  with  the  varnish  for  a  quarter  of 
an  hour,  they  add  a  quarter  of  an  ounce  of  Roman  vitriol  (sul- 
phate of  copper)  to  each  pound  of  varnish;  this  vitriol  they  have 
previously  dissolved  in  a  sufficient  quantity  of  water  (sometimes 
they  use  tea) ;  they  continue  to  stir  the  varnish  until,  as  I  have 
said,  the  bubbles  which  form  on  the  surface  show  a  violet  color; 
this  varnish,  thus  prepared,  is  called,  in  China,  Kouang-tsi,  or 
brilliant  varnish;  the  word  Kouang  means  brilliant. 


CHINESE  AND  JAPANESE  LACQUERS.  151 

Black  Varnish. — Within  a  few  years  the  Chinese  have  imitated 
the  brilliant  black  varnish  of  Japan.  This  the  Chinese  call  Yang- 
tsi;  Yang  signifies  the  sea,  as  though  to  say  a  varnish  which 
comes  from  over  seas,  Japan  being  separated  by  the  sea  from 
China. 

The  Yang-tsi  differs  from  the  Kouang-tsi  only  in  this,  that 
when  the  Kouang-tsi  is  entirely  evaporated  they  add  to  each 
pound  of  it  an  eighth  of  an  ounce  of  bone-black  made  from  the 
bones  of  a  deer,  reduced  to  a  fine  powder.  (The  Chinese  claim 
that  the  ribs  make  better  bone-black  than  the  other  bones.)  We 
tried  ivory-black;  the  workman  found  it  better  than  bone-black, 
and  begged  me  to  supply  him  with  it.  Besides  this  bone-black 
they  add  an  ounce  of  oil  of  tea,  which  they  render  siccative  by 
making  it  boil  gently,  after  having  thrown  into  it,  in  winter,  fifty 
grains  of  arsenic,  half  red  arsenic  or  realgar,  half  gray  or  white; 
in  summer  six  grains  are  enough;  they  stir  this  arsenic  constantly 
in  the  oil  with  a  spatula.  To  see  when  the  oil  has  become  suffi- 
ciently siccative  they  let  a  drop  fall  on  a  piece  of  cold  iron,  and  if, 
when  they  touch  the  tip  of  the  finger  to  this  thickened  oil,  it 
can  be  drawn  out  a  little  into  a  thread,  it  is  done.  This  oil  gives 
a  fine  brilliance  to  the  varnish. 

Tea-oil. — The  Chinese  say  that  no  other  oil  than  tea-oil  will 
dry  the  varnish,  and  that  any  other  oil  will  separate  from  it- — which 
I  doubt;  the  Tong-yeou  rendered  siccative  does  not  separate,  and 
I  believe  that  any  other  very  siccative  oil  would  have  the  same 
effect. 

This  tea-oil  is  made  from  the  fruit  of  a  particular  kind  of  a 
tea-tree;  it  resembles  our  plum-trees;  they  cultivate  it  only  for 
its  fruit  and  not  for  its  leaves.  This  fruit  resembles  our  chest- 
nut, except  that  the  outer  husk  does  not  bristle  with  points  like 
our  chestnut-burs.  The  fruit  of  the  Tong-chou,  from  which 
they  make  the  Tong-yeou,  resembles  it  also. 

The  Chinese  have  still  three  other  preparations  of  varnish, 
as  follows:  the  Tchao-tsi,  the  Kin-tsi,  and  the  Hoa-kin-tsi.  The 
Tchao-tsi  is  that  which  they  throw  upon  their  powdered  gold  to 
imitate  aventurine.  Tchao  means  to  envelop,  to  cover,  as  one 


152  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

would  say  an  exterior  varnish.  This  varnish  is  a  transparent 
yellow;  it  is  composed  of  half  Kouang-tsi,  that  is  to  say,  that 
which  comes  from  Kouang-tcheou-fou,  and  half  Tong-yeou 
rendered  siccative.  The  Kin-tsi  has  its  name  from  the  color  of 
gold;  the  word  Kin  means  gold.  In  fact,  this  varnish  is  of  a 
golden  yellow;  it  is  composed  of  the  most  common  Si-tsi,  or  that 
which  has  been  collected  as  the  third  crop,  half  varnish  and 
half  Tong-yeou.  It  is  upon  a  layer  of  this  varnish  that  they 
scatter  their  gold-powder,  over  which  they  spread,  as  I  have 
said,  a  coat  of  Tchao-tsi.  The  gold-powder  thus  set  between 
these  two  coats  of  varnish  imitates  aventurine;  but  it  is  only 
after  a  long  time,  for  it  is  much  more  beautiful  after  a  lapse  of 
years  than  it  is  within  a  few  months;  I  have  observed  it.  The 
Hoa-kin-tsi  is  that  which  is  used  by  painters  in  varnish  for  tem- 
pering their  colors,  whence  comes  the  name  Hoa,  which  means  to- 
paint;  that  of  Kin,  because  it  serves  or  painting  in  gold  or  for 
designs  in  gold:  the  varnish  is  composed  of  half  Tchao-tsi  and 
half  Kin-tsi. 

PREPARATION  OF  VARNISH. 

Straining. — The  first  thing  to  be  done  is  to  strain  the  varnish 
so  as  to  purify  it  as  much  as  possible  from  dust  and  sediment. 
For  this  purpose  they  prepare  some  cotton  as  if  to  make  a  counter- 
pane ;  they  spread  three  layers  of  cotton  thus  prepared  on  a  piece 
of  thin  cloth ;  on  these  layers  of  cotton  they  turn  the  varnish,  either 
Yang-tsi  or  Kouang-tsi  evaporated,  and  they  cover  it  very  accu- 
rately with  the  cotton,  layer  by  layer,  cutting  off,  if  it  is  necessary, 
in  the  folds,  a  little  of  the  cotton,  so  that  it  shall  lie  more  smoothly 
and  evenly.  When  the  three  layers  of  cotton  have  thus  been 
spread  upon  the  varnish,  one  after  another,  they  cover  the  whole 
with  the  cloth,  to  press  out  the  varnish  which  is  thus  wrapped  up. 
The  machine  which  the  Chinese  use  for  this  operation  is  very 
simple,  and  appears  to  me  convenient.  When  the  varnish  does  not 
trickle  out  any  more  they  open  the  cloth  and  with  their  fingers  pull 
to  pieces  the  three  layers  of  cotton,  so  as  to  be  able  to  press  out  as 
much  as  possible ;  they  repeat  this  manipulation  two  or  three  times. 


CHINESE  AND  JAPANESE  LACQUERS.  153. 

until  they  can  get  no  more  varnish  out;  finally  they  throw  away 
the  cotton  and  recommence  the  operation  with  three  other  layers  of 
new  cotton.  They  strain  the  varnish  a  third  time;  the  third  and 
last  time  they  do  not  use  cotton,  but  a  layer  of  See-mien.  The 
See-mien  is  made  of  the  outer  parchment  which  covers  the  chrysalis 
of  the  silkworm.  They  spread  upon  the  thin  cloth,  in  place  of 
cotton,  seven  or  eight  layers  of  See-mien ;  they  envelop  the  varnish 
as  they  did  before  when  they  used  cotton,  and  press  it  out.  The 
varnish  thus  filtered  is  reckoned  very  pure.  For  this  operation 
it  is  necessary  to  have  a  place  that  is  perfectly  clean,  where  there 
is  no  fear  of  dust,  so  that  at  the  end  there  shall  not  a  grain  of  dust 
fall  into  the  varnish  thus  purified.  The  Chinese  receive  it  as  it 
runs  out  from  the  filter  in  a  perfectly  clean  porcelain  vessel,  cover- 
ing the  vessel  with  a  sheet  of  the  paper  called  Maoteou-tchi,  which 
I  have  already  mentioned,  and  put  it  in  a  suitable  place  until  they 
wish  to  use  it,  when  they  do  not  wholly  uncover  the  vessel,  but 
only  raise  one  corner  of  the  paper  cover. 

APPLICATION  OF  THE   VARNISH. 

The  Workshop. — The  workshop  ought  to  be  an  extremely 
clean  place,  situated  where  it  will  be  as  much  as  possible  out  of  the 
way  of  dust;  to  secure  this  result  they  cover  the  wall  with  mats, 
and  over  these  mats  they  paste  paper  carefully  everywhere,  so  that 
one  cannot  discover  the  least  little  exposure  of  the  matting;  the 
very  door  of  the  workshop,  which  is  made  to  close  tightly,  is  cov- 
ered with  matting  and  papered  like  the  rest. 

Dust  is  Avoided. — When  the  workmen  have  to  apply  the 
varnish,  especially  the  finishing  coat,  if  the  weather  is  such  that 
there  is  no  fear  of  their  taking  cold,  they  wear  only  a  pair  of 
drawers,  not  even  a  shirt,  for  fear  of  bringing  dust  into  the  work- 
shop; if  the  season  does  not  permit  them  to  dispense  with  their 
clothing,  they  take  great  care  to  shake  off  the  dust  before  entering, 
and  they  wear  only  such  clothes  as  the  dust  will  not  easily  adhere 
to;  they  are  particular  to  avoid  any  disturbance  in  the  workshop,, 
and  no  unnecessary  persons  are  allowed  to  enter. 


154  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

The  first  thing  the  workmen  do  is  to  clean  the  brushes  which 
they  are  going  to  use.  They  have  a  little  bowl  with  a  little  oil  in 
it,  in  which  they  clean  them,  for  fear  that  there  may  be  some 
particles  of  dust  in  the  brushes;  they  test  them  carefully  before 
they  take  them  finally  from  the  oil.  The  brushes  being  perfectly 
clean,  they  uncover  a  corner  of  the  bowl  which  contains  the  var- 
nish which  has  been  thrice  filtered,  as  has  been  described.  In 
taking  the  varnish  on  the  brush  they  only  touch  it  to  the  top  of  the 
varnish,  and  in  withdrawing  the  hand  they  turn  the  brash  two 
or  three  times  to  break  off  the  thread  of  varnish  which  strings 
from  the  brush. 

In  spreading  the  varnish  it  is  necessary  to  pass  the  brush  in 
every  direction,  applying  it  equally  everywhere;  in  finishing  the 
brush  must  be  always  drawn  in  one  direction. 

Each  Coat  Dried  and  Rubbed. — Each  coa.  f  varnish  has  no 
greater  thickness  than  that  of  the  thinnest  paper ;  if  the  varnish 
is  too  thick  it  will  make  wrinkles  in  drying ;  it  is  troublesome  to  get 
rid  of  these ;  sometimes  one  is  even  obliged  to  cut  them  off  with  a 
chisel,  instead  of  the  easier  method  of  grinding  them  off  with 
cakes  made  of  brick-dust,  such  as  will  be  described  later.  Although 
it  may  not  actually  form  wrinkles,  such  a  coat  of  varnish  will  be 
very  troublesome  to  dry.  Before  the  application  of  a  second  coat 
of  varnish  it  is  necessary  that  the  first  coat  be  well  dried,  and 
should  ha've  been  polished  with  the  cakes  made  of  brick-dust. 

Moist  Air  Dries  Varnish. — In  order  to  se.  away  the  varnished 
pieces  to  dry  as  soon  as  they  are  varnished,  they  are  accustomed 
to  have  shelves  all  around  the  workshop  from  top  to  bottom ;  on 
these  they  place  the  varnished  articles,  setting  them  lower  or 
higher  according  as  they  wish  them  to  dry  more  or  less  quickly. 
The  humidity  of  the  earth  dries  them  more  or  less  rapidly  accord- 
ing as  they  are  set  nearer  or  farther  from  it.  When  they  are 
absolutely  dry  they  may  be  put  on  the  top  shelves,  and  left  there,  if 
it  is  thought  best.  At  Pekin,  where  the  air  is  extremely  dry,  it  is 
necessary,  to  dry  the  varnish,  to  put  it  in  a  humid  place,  sur- 
rounded by  matting  which  they  sprinkle  with  fresh  water;  other- 
wise the  varnish  will  not  dry.  If  it  is  an  article  which  is  so 


CHINESE  AND   JAPANESE  LACQUERS.  i$S 

situated  that  it  cannot  be  removed,  they  are  obliged  to  hang  wet 
cloths  about  it. 

When  the  first  coat  of  varnish  is  quite  dry  it  is  necessary  to 
polish  it ;  if  it  is  not  entirely  dry,  it  will  roll  up  in  places  when  they 
try  to  rub  it.  The  day  after  they  have  put  a  piece  to  dry  on  the  bot- 
tom shelf  they  examine  it  to  see  if  it  is  dry;  to  do  this  they  touch  it 
gently  with  the  tip  of  the  finger;  when  the  finger  is  withdrawn,  if 
the  varnish  is  felt  to  be  tacky  it  is  not  dry  enough  to  polish.  There 
is  no  risk  in  leaving  a  piece  several  days ;  the  drier  the  varnish  is 
the  better  it  will  polish.  It  is  only  necessary  to  be  careful,  in  damp 
weather,  that  the  varnish  should  not  be  too  moist;  for  then  it 
tarnishes  and  can  never  be  brought  back;  if  it  is  a  finishing  coat, 
it  is  lost:  it  is  necessary  to  rub  it  and  add  another  coat.  To  avoid 
this  inconvenience,  they  do  not  at  such  times  put  pieces  to  dry  on 
the  lowest  shelves,  but  on  the  second  or  third ;  it  is  better  that  the 
varnish  should  dry  slowly.  However  they  polish  the  foundation 
to  which  they  are  going  to  apply  the  varnish,  they  always  find 
some  little  inequalities,  which  one  or  two  coats  of  varnish  will  not 
be  able  to  efface;  this  is  why  they  are  obliged  to  rub  each  coat ;  the 
varnish  which  is  too  thin  is  liable  to  be  too  easily  removed.  What- 
ever care  they  take,  some  grains  of  dust  are  always  found  in  the 
varnish,  which  come  from  the  little  inequalities  removed  in  rub- 
bing; whence  it  follows  that  if  each  coat  were  not  rubbed,  the 
last  coat  would  be  imperfect. 

Polishing-powder. — To  rub  the  varnish  they  form  little 
cakes  composed  of  brick-dust  passed  through  a  fine  sieve  and 
washed  in  three  waters ;  after  stirring  it  in  water  until  it  is  turbid 
they  pour  it  off  into  another  vessel  and  throw  out  that  which  has 
settled  to  the  bottom,  as  too  coarse.  They  repeat  this  operation 
three  times,  and  then  leave  the  water  to  settle;  when  it  is  well 
settled  they  carefully  pour  off  the  water  and  cover  the  vessel 
which  contains  the  sediment,  and  set  it  in  the  sun  to  dry.  When 
dried  they  pass  it  through  a  fine  sieve,  they  mix  it  with  Tong-yeou, 
or  they  drop  in  some  Tou-tse  and  a  little  more  than  half  of  swine's 
blood  prepared  with  lime-water.  To  form  it  into  cakes  they  roll 
this  material  in  cloth,  give  it  the  form  they  wish;  and  finally  put  it 


1 56  TECHNOLOGY   OF   PAINT  AND    VARNISH. 

to  dry  in  the  shade  upon  a  plank  covered  with  paper;  if  they  put 
it  in  the  sun  to  dry,  they  shelter  it,  for  fear  that  some  coarse  parti- 
cles of  dust  may  fall  on  it  which,  in  polishing  the  varnish,  would 
make  scratches. 

The  preparation  of  the  swine's  blood  with  lime-water  is  made 
in  this  manner :  They  take  a  handful  of  straw,  beaten  and  coarsely 
chopped  in  pieces  three  or  four  inches  long ;  with  this  straw  they 
treat  the  blood  hi  the  way  pork-butchers  do  to  separate  the  clots 
of  blood;  after  which  they  pass  it  through  a  cloth,  and  a  little 
later  they  add  to  it  a  third  of  its  volume  of  lime-water  which  is 
white  with  lime,  not  having  been  allowed  to  settle.  This  milk 
of  lime  must  be  prepared  on  the  spot  and  immediately  added  to 
the  blood,  which  being  thus  prepared  is  preserved  in  a  covered 
earthen  vessel. 

Rubbing. — To  rub  the  varnish  they  wet  with  water  the  end  of 
the  cake  of  brick-dust,  and  they  rub  it  vigorously  all  over  the 
surface  to  remove  the  little  inequalities  caused  by  any  grains  of 
dust  which  may  have  been  in  the  varnish  or  in  the  brushes;  and 
from  time  to  time  they  pass  over  the  surface  a  brush  made  of 
long  hair,  wet  with  water,  holding  the  varnished  article  over  the 
vessel  in  which  they  wet  the  brush,  to  wash  off  and  remove  the 
mud  made  from  the  brick-dust,  so  as  to  see  if  there  are  still  any 
little  defects;  and  they  rub  them  away  before  they  apply  a  second 
coat  of  varnish.  They  rub  the  second  coat  like  the  first,  when 
it  is  thoroughly  dry;  at  last  they  apply  the  third  coat;  it  is 
above  all  things  important  with  this  last  coat  to  take  all  possible 
care  to  avoid  the  least  dust. 

It  is  only  within  a  few  years,  under  the  reigning  emperor, 
that  the  secret  of  the  Yang-tsi,  or  the  varnish  which  imitates  the 
brilliance  of  that  of  Japan,  has  been  known  outside  of  the  palace. 
About  thirty  years  ago  a  private  citizen  of  Sout-cheou,  one  of 
the  cities  where  they  make  the  very  finest  varnished  pieces  in 
China,  found  out  the  secret,  or  rather  learned  it  from  some  Japan- 
ese, the  merchants  of  Sout-cheou  having  trade  with  those  of 
Japan.  It  is  to  be  wished  that  they  had  also  learned  the  secret  of 
preparing  their  Tchao-tsi,  which  surpasses  infinitely  that  of  China* 


CHINESE  AND   JAPANESE  LACQUERS.  157 

The  Emperor  Yong-Toking,  father  of  the  emperor  now  reigning, 
wished  to  keep  it  a  secret,  and  did  not  wish  that  it  should  go  out 
of  the  palace;  in  fact,  the  secret  remained  unknown  to  the  people 
outside  for  many  years.  At  last  Kien-long,  now  reigning,  was 
not  so  careful  about  varnish  as  his  father,  and  did  not  prevent 
the  secret  from  being  known  outside  the  palace.  I  know  one 
of  the  workmen  who  worked  in  the  palace,  who  has  done  in  my 
presence  the  things  I  have  written  in  this  memoir;  it  is  from 
this  same  workman,  who  has  worked  for  three  months  in  our 
house,  that  I  know  what  I  have  written  about  varnish.  He  is  a 
Christian  and  my  convert;  I  have  reason  to  believe  that  he  does 
not  deceive  me. 

Polishing. — Formerly  the  Chinese  made  only  the  varnish 
which  they  call  Toui-kouang;  Kouang  means  brilliance,  and  Toui 
to  remove,  as  they  say  of  varnish  which  has  lost  its  lustre;  the 
reason  being  that  they  rubbed  the  last  coat  of  varnish  the  same 
as  the  others,  and  in  that  way  got  rid  of  its  gloss.  To  partly 
restore  this,  after  having  carefully  rubbed  this  third  coat  they 
gave  it  second  rubbing  with  a  bunch  of  hair  which  had  been  wet 
in  water  in  which  they  had  suspended  some  very  fine  powder; 
after  this  they  rubbed  it  with  a  piece  of  very  soft  silk  cloth,  and 
with  this  in  the  hand  they  rubbed  vigorously,  until  the  varnish 
became  bright.  In  the  places  which  they  could  not  reach  with 
the  hand,  they  attached  to  the  end  of  a  bit  of  wood  a  piece  of 
this  soft  silk,  and  with  this  rubbed  it;  and  finally  they  rubbed 
the  varnished  surface  with  a  bit  of  silk  slightly  moistened  with 
some  clear  oil,  no  matter  what  kind;  this  gave  the  varnish  a  little 
gloss,  but  not  to  be  compared  with  that  of  the  varnish  called 
Yang-tsi. 

The  Yang-tsi,  on  account  of  the  oil  of  tea  which  is  combined 
with  it  and  which  gives  it  its  brilliance,  cannot  be  rubbed;  it  is 
therefore  still  more  necessary  to  avoid  dust  than  when  using 
Toui-kouang.  The  only  remedy  is  to  hide  the  defects,  in  painting 
the  varnished  articles,  by  making  the  design  conceal  these  imper- 
fections. 

In  varnishing  with  Yang-tsi  they  employ  this  beautiful  varnish 


158  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

'Only  for  the  finishing  coat.  The  Kouang-tsi,  of  which  they  make 
the  Toui-kouang,  is  perfectly  good  for  the  two  under  coats,  because 
these  have  to  be  rubbed.  The  last  coat  of  varnish  ought  espe- 
cially to  remain  a  long  time  on  the  shelves  at  the  top  of  the  work- 
shop, for  at  least  fifteen  days,  before  any  painting  is  done  on  it ;  there 
is  a  chance  that  the  varnish  will  be  sticky;  the  gold  will  stick  to 
the  places  which  are  not  entirely  dry. 

Observe  that  when  one  would  make  the  beautiful  varnished 
boxes,  like  those  of  the  Japanese,  it  will  not  do  to  have  them  liable 
to  open  at  the  joints;  it  is  necessary  to  cover  all  the  joints  with 
strips  of  the  paper  called  Che-tan-tchi.  The  Japanese  use  it,  as 
well  as  the  Chinese,  to  make  their  work  more  substantial;  but 
in  China,  where  they  do  not  care  so  much  for  the  excessive  light- 
ness of  these  boxes,  they  use  a  sort  of  canvas  made  of  silk,  called 
Kieun,  in  place  of  Che-tan-  tehi ;  then  their  boxes  will  never  come  to 
pieces. 

Preparation  of  the  Surface. — To  prevent  the  varnish  of  the 
first  coat  from  sinking  into  the  wood  they  brush  the  piece  over 
first  with  gum- water  mixed  with  chalk.  The  Che-tan-tchi  or  the 
Kieun  are  applied  with  pure  varnish  not  evaporated.  Before 
putting  on  the  first  coat  it  is  necessary,  with  a  piece  of  stone  less 
harsh  than  sandstone,  to  rub  well  the  Che-tan-tchi  or  the  Kieun; 
to  make  their  surface  more  uniform,  after  they  have  been  rubbed, 
they  are  obliged  to  lay  on  a  light  coat  of  the  composition  of  brick- 
dust  which  I  have  already  described,  immediately  before  the  appli- 
cation of  the  varnish,  which  they  mix  with  a  half  of  Tout-tsi. 
(Note.  Tou  signifies  earth,  tsi  signifies  grain;  as  though  to  say, 
grains  of  earth;  or  rather,  earth  which  is  in  granular  form;  they 
find  it  in  abundance  in  the  mountains.) 

It  is  necessary  that  the  Tout-tsi  should  be  passed  through  a 
sieve;  the  whole  is  mixed  with  varnish  not  evaporated,  when  the 
composition  is  very  clear  and  well  finished.  The  Japanese  some- 
times employ  only  the  Che-tan-tchi,  and  content  themselves  with 
rubbing  the  pieces,  before  applying  the  first  coat  of  varnish,  with 
wax,  to  prevent  the  varnish  from  penetrating  the  wood.  The 
Chinese  sometimes  do  the  same  thing;  but  articles  finished  in  this 


CHINESE  AND   JAPANESE  LACQUERS.  159 

way  are  not  substantial,  and  are  liable  to  crack  at  the  joints,  espe- 
cially at  Pekin,  where  the  air  is  extremely  trying  to  wood,  no 
matter  how  old  it  may  be. 

The  wood  which  the  Chinese  use  for  making  these  varnished 
articles  is  as  light  as  that  used  by  the  Japanese,  and  if  the  work  of 
the  Chinese  is  heavier  than  that  made  in  Japan,  it  is  because  the 
Chinese  usually  send  their  best  work  to  Pekin,  and  wish  them  to 
be  substantial,  fearing  that  they  will  not  stand  the  climate  of  Pekin, 
where,  in  spite  of  all  precautions,  they  will  not  last  unless  they  are 
built  as  solidly  as  those  which  are  made  in  Pekin  itself. 

The  wood  which  the  Chinese  employ  is  called  Ngou-tou-mou. 
Mou  is  the  generic  name  for  wood;  Ngou-tou  is  the  name  of  the 
trees.  Its  wood  is  very  pliant  and  extremely  light,  excellent  for 
musical  instruments ;  they  claim  that  it  will  give  out  a  better  sound 
than  any  other  wood. 

The  brushes  for  applying  the  varnish  are  made  of  hair;  those 
which  are  used  to  wash  the  pieces  are  made  of  the  beards  of  she- 
goats,  or  they  can  use  that  from  cows'  tails.  The  paste  with 
which  they  bind  together  the  hair  of  the  brushes  is  made  of  Tong- 
yeou,  litharge,  and  Tou-tse,  which  makes  a  compound  that  dries 
very  quickly.  To  this  mixture  they  add  a  half  of  the  swine's 
blood  treated  with  lime-water.  Another  composition  may  be  used 
for  the  same  purpose,  provided  that  it  is  elastic  and,  in  working, 
does  not  crumble  and  come  out  in  dust,  as  sometimes  happens  to 
our  brushes  in  Europe. 

If,  in  using  varnish,  it  sticks  to  the  hands,  they  rub  them  with 
a  little  oil;  it  is  easily  removed. 

It  sometimes  happens  in  time  of  rain  or  of  high  winds  that 
the  varnish  does  not  dry;  if  it  does  not  dry  in  the  usual  time,  it 
never  will  dry.  Then  the  only  remedy  is  to  rub  it  with  lime  and 
set  it  on  the  lower  shelves  of  the  workshop;  it  will  dry  in  a  short 
time.  Before  putting  it  away  to  dry,  it  is  necessary  to  thoroughly 
wipe  off  the  lime  with  a  piece  of  silk.  If  the  lime  has  not  entirely 
removed  the  varnish  which  did  not  dry,  it  will  raise  up  a  quantity 
of  little  points;  these  must  be  made  to  disappear  in  polishing  the 
article,  after  which  another  coat  of  varnish  is  to  be  applied. 


160  TECHNOLOGY  OF  PAINT  AND    VARNISH, 

If,  in  the  winter,  they  wish  to  evaporate  the  varnish,  as  there 
is  little  heat  from  the  sun,  and  the  operation  would  require  a 
long  time,  they  proceed  thus :  They  roll  up  a  mat  into  the  form  of 
a  muff,  of  the  size  of  the  vessel  in  which  they  wish  to  evaporate 
the  varnish.  They  set  the  mat  upright,  and  place  at  the  bottom 
a  chafing-dish  with  a  little  fire  in  it,  and  a  foot  or  a  foot  and  a 
half  above  it  they  support,  by  means  of  a  tripod,  the  dish  of 
varnish ;  in  an  hour  or  an  hour  and  a  half  the  varnish  is  evaporated, 
all  the  watery  part  is  gone. 

In  rendering  the  Tong-yeou  siccative,  after  having  drawn  it 
from  the  fire,  when  they  judge  this  oil  to  be  sufficiently  siccative, 
while  it  is  yet  warm,  coming  from  over  the  fire,  they  decant  it 
many  times  to  disperse  the  fumes  which  come  from  it;  without 
this  precaution  the  Chinese  tell  us  that  it  will  give  a  bad  color  to 
varnish. 

PAINTING   ON   VARNISH. 

Painting  on  varnish  is  suitable  only  for  furniture  like  tables, 
chairs,  cabinets,  and  the  like;  for  large  articles  which  one  does 
not  look  at  too  closely  it  produces  a  good  effect;  but  for  small 
articles  which  require  delicate  designs  it  is  not  well  adapted;  it 
should  therefore  be  confined  to  furniture  and  on  the  inside  of 
boxes,  especially  large  ones. 

Only  designs  in  gold  are  fit  for  delicate  work.  However 
finely  finished  may  be  the  gold-work  on  varnish  done  in  China, 
it  is  not  comparable  with  the  beautiful  work  which  is  made  in 
Japan.  Up  to  the  present  time  the  Chinese  have  not  found  the 
secret  of  the  water-white  varnish  which  the  Japanese  apply  over 
their  gold  designs.  The  transparent  varnish  of  China,  which 
they  call  Tchao-tsi,  inclines  to  a  yellow  color,  but  a  muddy  yellow, 
so  that  it  cannot  be  used  for  fine  and  delicate  designs ;  it  may  be 
used  to  imitate  aventurine,  as  I  have  already  remarked;  but  this 
aventurine  does  not  compare  with  that  of  Japan.  I  am  not 
without  hope  that  eventually  we  may  invent  in  France  some 
varnish  which  can  be  applied  over  the  Chinese  varnish;  and 


CHINESE  AND  JAPANESE  LACQUERS.  161 

then  we  will  be  able  to  compete  with  and  even  surpass  the  Japan- 
ese, our  European  designs  being  much  finer  than  those  of  Japan. 

Designs  are  Transferred. — The  following  are  the  details  of 
painting  on  varnish,  as  it  is  done  in  China.  In  the  first  place, 
the  master  painter  makes  his  design,  the  outlines  of  which  he 
sketches  on  paper  with  crayon,  and  then  fills  in  the  details  with 
a  brush  and  ink.  Upon  this  design  the  pupils  follow  all  the 
strokes  of  the  brush  with  orpiment,  distempered  with  water; 
and,  to  imprint  the  design  upon  the  varnished  article,  they  apply 
to  it  this  design  thus  freshly  traced,  pressing  lightly  with  the 
fingers  everywhere  over  the  design,  in  order  that  all  the  marks 
should  leave  impressions  upon  the  work.  Having  taken  off  the 
paper  they  use  orpiment  again,  but  mixed  in  gum-water,  or  in 
water  in  which  a  little  glue  has  been  dissolved  (where  we  use 
gum- water  the  Chinese  use  size),  going  over  all  the  marks  with 
a  brush;  then  the  design  will  not  come  off. 

I  have  already  said  that  the  varnish  employed  by  painters  in 
varnish  is  called  Koa-kin-tsi;  it  is  this  varnish  which  is  used  for 
a  mordant  in  applying  gold;  also  this  varnish  is  used  for  dis- 
tempering colors.  To  render  the  varnish  more  fluid  they  mix 
with  it  a  little  camphor,  which  they  have  previously  crushed  and 
mixed  with  some  varnish;  they  make  a  paste  of  it  which  they 
knead  or  rub  with  a  spatula  a  quarter  of  an  hour  or  so;  it  is  this 
paste  of  which  they  take  a  little  to  temper  their  colors.  Their 
mordant  is  nothing  else,  as  has  been  said,  than  the  varnish  Koa- 
kin-tsi,  to  which  they  add  some  orpiment;  when  the  colors  are 
well  mixed  they  strain  them  through  Che-tan- tschi;  they  take 
commonly  a  little  at  a  time,  perhaps  an  eighth  of  an  ounce  or 
so,  enveloping  it  in  Che-tan-tschi,  and  twisting  the  two  ends  with 
the  fingers,  they  receive  the  color  as  it  comes  through  on  their 
fingers  with  which  they  are  twisting  it*;  they  scrape  it  off  on  the 
palette,  which  is  only  a  piece  of  bamboo  split  in  two  in  the  middle ; 
often,  before  they  are  done,  the  paper  bursts.  They  ought,  as 
soon  as  the  color  begins  to  come  through,  to  untwist  the  paper 
a  little  without  slackening  the  hands,  but  with  one  of  the  dis- 
engaged fingers  transfer  the  color  as  \J:  exudes  to  the  place  where 


162  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

it  is  to  be  received,  being  careful  not  to  open  the  paper;  in  this 
way  the  paper  may  usually  be  prevented  from  bursting. 

If  they  wish  the  gold  to  have  a  high  color,  they  mix  vermilion 
with  the  mordant;  after  the  application  of  the  mordant  they  set 
the  piece  to  dry  in  the  workshop;  about  twelve  hours  is  enough 
for  the  mordant  to  be  dry  enough  for  the  application  of  the  gold. 

Gilding. — They  have  carefully  prepared  powdered  gold  in  a 
shell,  which  they  apply  with  brushes  of  See-mien;  with  these 
they  rub  the  gold  lightly  over  the  place  where  there  is  mordant; 
brushing  off  the  surface,  they  find  the  gold  applied  to  the  design. 
If  they  fear  lest  it  may  stick  to  places  where  they  have  not  applied 
the  mordant,  on  account  of  the  varnish  not  being  sufficiently 
dry,  they  crush  some  ball  white,  and  with  a  bit  of  silk  cloth  they 
rub  it  lightly  over  the  suspected  places;  after  having  well  wiped 
the  surface  they  boldly  apply  the  gold  upon  the  mordant. 

Sometimes  the  painters  do  not  put  to  dry  in  the  workshop  the 
pieces  on  which  they  have  applied  the  mordant.  They  have  a 
paper  called  Tchou-tchi,  which  is  made  of  the  pellicle  which  covers 
the  joints  of  the  bamboo;  it  is  made  in  great  quantity  in  China: 
the  most  of  the  books  are  printed  on  this  paper;  that  which  is 
used  for  the  purpose  now  mentioned  is  very  thin — the  same 
which  is  used  for  books  of  gold-leaf.  This  they  apply  several 
times  over  the  mordant,  until  hardly  any  trace  of  it  remains; 
then  they  apply  the  shell  gold,  which  adheres  in  greater  quan- 
tity but  with  less  lustre;  for  shading  it  is  good,  but  elsewhere 
it  is  better  to  apply  it  in  the  other  manner. 

The  Chinese  use  three  kinds  of  gold,  the  Ta-tchi,  the  Tien- 
tchi,  and  the  Hium-tchi.  The  Ta-tchi  is  ordinary  gold;  the 
Tien-tchi  is  pale  gold ;  the  Hium-tchi  is  made  with  silver-leaf  to 
which  they  have  given  a  golden  color  by  exposing  it  to  the  vapor 
of  sulphur.  The  Hium-tchi  is  not  much  used  except  for  the  edges 
of  dishes,  and  sometimes  for  unusually  pale  shades;  to  gild  the 
edges  of  vessels  they  pass  the  Hium-tchi  through  a  sieve,  and 
with  the  end  of  the  finger,  on  which  they  have  placed  some  of 
this  powder,  they  apply  it  on  the  edges  where  they  have  just 
before  applied  some  mordant  without  using  any  Tchou-tchi  to 


CHINESE  AND   JAPANESE  LACQUERS.  163 

take  it  up ;  this  is  so  that  there  may  be  a  large  amount  on  those 
places  which  are  most  subject  to  wear;  they  do  not  care  if  the 
mordant  does  dull  the  gold. 

When  they  have  been  over  the  article  with  -the  bunch  of  See- 
mien,  charged  with  shell  gold,  sometimes  a  little  gold  adheres  to 
the  surface  without  being  really  attached;  this  they  brush  off  by 
lightly  touching  it  with  the  bunch  of  See-mien.  If  there  are  any 
places  which  they  cannot  reach  with  the  bunch  of  See-mien,  they 
apply  the  gold  with  the  pointed  end  of  the  brush-handle. 

To  imitate  mountains,  and  make  sharp  separations,  they  cut 
out  a  bit  of  Tchou-tchi  according  to  the  form  which  they  wish  to 
give  the  mountain;  with  the  paper  they  cover  the  place  of  the 
mountain  and  pass  the  pale  gold  over  the  whole;  it  does  not 
adhere  to  the  places  covered  by  the  paper. 

To  imitate  the  trunks  and  branches  of  trees  or  the  stalks  of 
plants,  after  having  laid  on  the  first  coat  of  gilding,  they  trace 
anew  the  places  which  they  wish  to  be  marked;  and  when  the 
mordant  has  dried  in  the  workshop  twelve  hours  they  go  over 
it  with  shell  gold.  Ordinarily  they  use  the  red  mordant,  that  is, 
that  in  which  they  have  mixed  vermilion  instead  of  orpiment; 
the  gold  is  thus  made  brighter  in  color. 

White  in  varnish  is  obtained  by  mixing  with  varnish  leaves 
of  silver;  only  enough  varnish  is  used  to  make  a  paste.  As 
much  varnish  as  will  make  the  bulk  of  a  pea  is  enough  for  twenty 
leaves  of  silver;  they  mix  the  leaves  one  after  another;  when  all 
are  mixed  they  add  a  little  camphor,  which  makes  the  paste  almost 
as  clear  as  water.  In  place  of  silver-leaf,  to  be  economical,  the 
Chinese  sometimes  use  some  quicksilver,  prepared  in  a  particular 
manner.  This  is'a  secret  in  a  single  family.  All  other  material 
than  silver-leaf  or  the  mercury  thus  prepared  will  blacken 
when  mixed  with  varnish;  silver  makes  the  most  beautiful 
white. 

Varnish  Colors. — For  red  they  use  Tchou-tche,  which  appears 
to  be  the  mineral  cinnabar.  They  can  also  use  a  lake  made 
of  carthamus-flowers. 

For  green  they  use  orpiment,  which  they  mix  with  indigo. 


1 64  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

which  they  call  here  Kouang-tien-hoa ;  it  is  true  indigo  and  comes 
from  the  southern  provinces. 

For  violet  they  use  Tse-che,  or  violet-stone  (Che  means  stone ; 
Tse,  violet) ;  they  use  it  to  make  opaque  glass.  They  reduce  this 
stone  to  an  impalpable  powder.  They  also  use  colcothar,  or 
green  vitriol  calcined  until  it  is  red;  to  free  it  from  saline  matter 
they  boil  it  in  a  large  quantity  of  water.  Varnish,  they  say,  will 
not  endure  any  salt. 

Yellow  is  made  with  orpiment. 

Colors  mixed  with  varnish  are  not  brilliant  at  once,  but  change 
after  a  time ;  the  older  they  are  the  more  beautiful  they  become. 

When  painters  wish  to  lay  on  an  unusually  heavy  coat  of 
color  they  use  See-mien  instead  of'Tchou-tchi. 

To  clean  varnished  articles  they  use  a  piece  of  silk,  like  an 
old  silk  handkerchief;  with  this  they  dust  off  the  surface  by 
whisking  it,  not  by  rubbing;  if,  after  this,  there  are  still  some 
dirty  spots,  they  easily  clean  them  by  wrapping  the  finger  in  the 
handkerchief  and  rubbing  them;  if  that  is  not  enough,  they  may 
wet  the  end  of  the  finger,  still  wrapped  in  the  handkerchief,  by 
touching  it  to  the  tongue;  but  it  is  best  if  possible  to  dust  off 
the  dirt  with  the  wind  made  by  using  the  handkerchief  as  a 
whisk,  and  if  that  will  not  do,  pass  the  finger,  wrapped  in  the 
handkerchief,  through  the  hair,  from  which  it  will  absorb  a  little 
oil,  which  is  excellent  for  cleaning  the  varnished  surface. 

If  the  varnished  article  has  been  softened  by  being  set  too 
near  the  fire,  it  may  be  restored  by  leaving  it  out  in  the  dew. 

By  exposing  colors  in  varnish  to  the  air,  their  brilliance  is 
increased. 

Shell  gold  is  thus  prepared:  They  roll  a  sheet  of  paper  into  a 
cone;  in  this  they  put  the  gold-leaf  which  is  to  be  made  into 
shell  gold.  When  they  have  enough,  they  take  a  very  smooth 
plate  or  porcelain  platter;  on  this  they  pour  a  few  drops  of  water 
in  which  they  have  dissolved  a  little  glue ;  then  they  turn  the  gold- 
leaf  on  the  plate,  and  with  the  ends  of  the  fingers  they  rub  the 
gold  as  if  with  a  muller;  the  more  they  rub  it  the  more  beautiful 
it  becomes.  They  wash  it  twice  with  slightly  warm  water,  and 


CHINESE  AND  JAPANESE  LACQUERS.  165 

put  it  away  for  use.    This  is  the  only  way  the  Chinese  have  for 
preparing  it. 

From  Father  D'Incarville's  memoir  there  is  an  interval  of  a 
century  and  a  quarter  to  the  next  detailed  account  of  oriental 
lacquer,  this  time  by  a  British  acting  consul,  Mr.  John  J.  Quin, 
who  in  January,  1882,  wrote  from  Tokio  a  paper  of  the  highest 
interest  on  the  subject;  it  is  evident  from  what  he  says  that  the 
varnish  must  have  been  the  same  as  that  used  in  China;  but  the 
methods  of  using  varnish  were  far  more  elaborate  than  those 
described  by  the  Jesuit  missionary.  It  is  not  improbable  that 
D'Incarville  gave  only  the  simplest  procedure,  and  that  more 
intricate  methods  were  in  use*;  in  fact,  we  know  that  such  must 
have  been  the  case.  As  described  by  Mr.  Quin  the  processes 
are  much  more  prolonged;  but  he  only  gives  what  was  in  his 
view  the  simplest  practice.  The  following  is  condensed  from 
his  paper,  using  wherever  possible  his  own  words;  but  the  neces- 
sary omissions  have  made  it  seem  necessary  to  change  the  language 
in  many  places,  that  the  meaning  may  be  clear.  Those  interested 
may  consult  the  original  paper  in  the  British  consular  reports. 

Lacquer-trees  of  Japan. — The  Rhus  vernicifera,  the  lac- 
quer-tree of  Japan,  is  met  with  all  over  the  main  island,  and 
also  in  smaller  quantities  in  Kinshiu  and  Shikoku,  but  it  is  from 
Tokio  northward  that  it  principally  flourishes,  growing  freely  on 
the  mountains  as  well  as  in  the  plains,  thus  indicating  that  a 
moderate  climate  suits  the  tree  better  than  a  very  warm  one. 
Since  early  days  the  cultivation  of  the  trees  has  been  encouraged 
by  the  government,  and  as  the  lacquer  industry  increased  planta- 
tions were  made  in  every  province  and  district. 

The  lacquer-tree  can  be  raised  by  seed  sown  in  January  or 
February;  in  ten  years  the  seedling  trees  will  average  ten  feet 
high,  the  diameter  of  its  trunk  two  and  one-half  to  three  inches, 
and  its  yield  of  lacquer  sufficient  to  fill  a  three-ounce  bottle.  The 
trees  are  set  about  six  feet  apart  in  the  plantations. 

A  more  common  method  is  to  cut  off  a  piece  six  inches  long 
and  the  thickness  of  a  ringer  from  the  root  of  a  vigorous  young 


i66  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

tree,  and  planted  with  one  inch  of  the  root  above  ground.  In 
ten  years  tfyese  will  make  trees  larger  than  the  seedlings  by  about 
two- thirds  and  will  yield  nearly  half  as  much  more  sap. 

Lacquer  plantations  are  only  on  hillsides  and  waste  lands. 

Collecting  Lacquer. — The  trees  are  tapped  once  in  four  days 
for  twenty-five  times  in  one  season  from  June  ist  to  October  ist. 
The  cuts  are  each  about  an  inch  and  a  half  long  and  are  from  near 
the  ground  to  as  high  as  a  man  can  reach  about  six  inches  apart 
vertically,  but  diagonally,  not  one  above  another.  Branches 
one  inch  or  more  in  diameter  are  also  tapped.  The  tree  is  thus 
destroyed  in  one  year.  When  cut  down  the  branches  are  cut  up 
and  tied  in  bundles  and  steeped  in  water  for  ten  days,  after  which 
the  lacquer  which  exudes  from  them  is  scraped  off;  this  is  called 
Seshime,  or  branch  lacquer;  but  this  name  is  also  applied  to 
purified  and  filtered  raw  lacquer  obtained  from  the  trunks  of  the 
trees,  as  has  been  fully*  explained  by  Rein,  and  in  the  following 
directions,  where  the  term  "branch  lacquer"  is  used,  this  purified 
raw  lacquer  is  undoubtedly  meant.  The  confusion  arises  from 
the  same  name,  se-shime,  being  applied  specifically  to  branch 
lacquer  and  generally  to  purified  raw  lacquer.  Only  a  small 
amount  of  true  branch  lacquer  is  obtained,  and  it  is  of  poor  quality; 
while  from  Mr.  Quin's  specifications  it  is  plain  that  most  of  the 
varnish  used  was  what  he  calls  "branch  lacquer,"  really  the 
ordinary  se-shime. 

Shoots  sprout  up  from  the  roots  of  the  trees  which  have  been 
cut  down,  and  grow  rapidly. 

The  best  lacquer  for  transparent  varnish  comes  from  large  trees > 
one  to  two  hundred  years  old.  These  are,  however,  rapidly  dis- 
appearing. These  large  trees  were  formerly  valuable  because 
wax  was  made  from  their  berries,  and  this  was  used  for  lighting; 
the  introduction  of  kerosene  has  destroyed  this  industry. 

True  branch  lacquer  becomes  extremely  hard  when  once 
dry,  but  used  alone  will  not  dry  under  some  twenty  days,  so  that 
now,  when  time  is  an  object,  the  pure  sap  is  very  little  used. 
The  price  of  pure  branch  lacquer  is,  owing  to  the  difficulty  of 
drying,  only  70  per  cent,  of  ordinary  good  lacquer. 


CHINESE  AND  JAPANESE  LACQUERS. 

Evaporating  in  the  Sun. — In  preparing  all  lacquer — from  the 
crude  lacquer  to  the  various  mixtures — the  principal  object  is 
to  get  rid  of  the  water  that  exudes  from  the  tree  with  the  sap. 
To  effect  this,  it  is  exposed  in  broad  flat  wooden  dishes,  and 
stirred  in  the  sun.  This,  however,  alone  will  not  cause  the  original 
water  to  evaporate,  so  from  time  to  time,  ordinarily  about  three 
times  in  the  day,  a  small  portion  of  clear  water  is  stirred  in,  say 
one  per  cent,  each  time,  for  a  couple  or  three  days,  according  to 
the  heat  of  the  sun;  all  the  water  then  evaporates  together.  No 
lacquer  will  dry  until  this  process  has  been  gone  through.  If 
the  lacquer  is  old,  i.e.,  has  been  tapped  a  long  time  before  using, 
it  is  much  more  difficult  to  dry.  In  such  cases  a  portion  of  fresh 
lacquer  is  added  to  the  old  by  the  wholesale  dealers;  or  else  the 
manufacturers,  instead  of  water,  sometimes  mix  sake  (rice  beer) 
or  alcohol  to  quicken  it. 

A  very  remarkable  property  of  lacquer  should  be  mentioned. 
If  crude  lacquer,  which  is  originally  of  the  color  and  consistency 
of  cream,  is  exposed  to  the  sun  a  few  days  without  adding  water,  it 
loses  its  creamy  color,  and  becomes  quite  black,  or  nearly  so,  but 
also  becomes  thinner  and  transparent,  or  rather  translucent,  as 
can  be  seen  when  it  is  smeared  on  a  white  board.  It  will  not  now,' 
however,  dry  if  applied  to  an  article,  even  if  kept  a  month  or  more 
in  the  damp  press.  But  if  water  is  mixed  with  the  lacquer  which 
has  thus  been  exposed  and  become  black,  it  at  once  loses  its  black 
color  and  its  transparency,  and  becomes  again  of  a  creamy  color, 
though  slightly  darker,  as  if  some  coffee  had  been  added,  than  at 
first.  After  evaporating  this  water  it  can  then  be  used  like  any 
ordinary  lacquer,  either  alone  or  in  mixtures,  and  will  dry  in  the 
damp  press,  during  which  process  it  again  turns  black. 

Black  Lacquer.  Black  lacquer  is  made  by  adding  to  crude 
lacquer  about  five  per  cent,  of  the  tooth-dye  used  by  women  to 
blacken  their  teeth,  which  is  made  by  boiling  iron- filings  in  rice 
vinegar,  and  exposing  it  to  the  sun  for  several  days,  stirring  the 
mixture  frequently  until  it  becomes  a  deep  black. 

What  lacquer-workers  have  found  their  greatest  stumbling- 
block  is  the  difficulty  of  obtaining  a  clear  transparent  varnish. 


168  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

What  is  called  a  transparent  varnish  is  really  black  to  the  eye 
and  requires  grinding  and  polishing  after  application  before  it 
presents  a  brilliant  surface,  becoming  also  much  lighter  after  a 
little  time. 

Perilla-oil. — Only  the  cheapest  and  commonest  kinds  of  lac- 
quering are  done  with  lacquer  mixed  with  oil;  the  oil  used  is 
that  obtained  from  the  plant  called  Ye  (Perilla  ocymoides). 
These  do  not  admit  of  polishing.  Lacquer  is  prepared  in  this 
way,  sometimes  as  much  as  fifty  per  cent,  of  oil  being  added, 
after  which  water  is  added  and  the  whole  evaporated  again  in  the 
sun ;  and  this  is  used  to  mix  with  colors  to  make  enamel  paints.  It 
is  said  that  vegetable  colors  cannot  be  used  with  lacquer,  being 
in  some  way  destroyed  by  it.  The  workmen  have  never  been 
able  to  produce  white,  purple,  or  any  of  the  more  delicate  shades. 
Vermilion,  oxide  of  iron,  and  orpiment  are  the  principal 
colors. 

For  preparing  the  surface  to  be  lacquered  various  priming 
coats  are  used;  cavities  are  filled  with  a  sort  of  cement  made 
by  mixing  chopped  hemp  fibre  with  lacquer;  joints  are  covered 
with  hemp  or  silk  cloth,  which  is  pasted  on  with  a  mixture  of 
wheat-flour  paste  and  branch  lacquer,  or  instead  of  wheat-flour 
paste,  rice-flour  paste  is  used,  but  is  not  as  good.  A  mixture  of 
whiting  and  liquid  glue  is  used  for  a  surface  coat  on  cheap  articles. 
Surfacing  compounds,  like  our  rough-stuff,  are  made  by  mixing 
lacquer  with  finely  powdered  brick-dust,  or  powder  made  of  some 
fine  clay  which  has  been  burned.  They  have  rubbing- stones  of 
four  degrees  of  fineness;  also  they  use  scouring- rushes.  (Equise- 
tum)  in  place  of  sandpaper;  they  use  several  grades  of  charcoal 
for  polishing,  or  rather  for  rubbing  before  polishing;  for  a  polish- 
ing-powder  they  calcine  deer's  horns  and  reduce  them  to  a  very 
fine  powder. 

The  process  of  plain  lacquering  may  be  thus  described : 

1.  The  article  to  be  lacquered  is  first  carefully  smoothed. 

2.  The  wood  is  slightly  hollowed  away  along  each  joint,  so  as  to 
form  a  circular  depression. 

3.  The  surface  of  the  whole  article  is  then  given  a  coating  of 


CHINESE  AND   JAPANESE  LACQUERS.  169 

branch  lacquer,  and  the  article  set  to  dry  in  the  .damp  press  for 
about  twelve  hours.  This  press  is  air-tight,  made  of  wood,  with 
rough  unplaned  planks  inside;  these  are  thoroughly  wetted  with 
water  before  the  articles  are  put  in  to  dry.  Lacquer  absolutely 
requires  a  damp  closed  atmosphere  for  its  hardening;  otherwise 
it  will  run  and  will  always  remain  sticky.  The  time  of  drying  is 
from  six  to  fifty  hours,  according  to  the  kind  of  lacquer  and  the  time 
of  year. 

4.  The  hollowed  portions  are  filled  with  a  mixture  of  finely 
chopped  hemp,  rice  paste,  and  branch  lacquer;  this  is  well  rubbed 
in  with  a  wooden  spatula,  and  the  piece  is  set  in  the  damp  press 
to  dry  for  at  least  forty  hours. 

5.  Over  this  is  spread  a  coating  made  of  two  parts  of  finely 
powdered  burnt  clay  and  one  and  a  half  parts  of  branch  lacquer, 
in  with  just  enough  water  to  mix  the  clay  to  a  paste ;  it  is  then  set 
to  dry  for  twelve  hours. 

6.  The  next  process  is  to  smooth  off  with  a  rubbing-stone 
any  roughness  of  the  preceding  coats. 

7.  The  article  is  then  given  a  coating  of  a  mixture  of  wheat- 
flour  paste  with  branch  lacquer,  over  which  is  stretched  a  hempen 
cloth,  great  care  being  taken  to  spread  it  smoothly  and  leave  no 
wrinkles  or  perceptible  joinings;  and  it  is  then  again  inclosed  in 
the  drying-press  for  twenty-four  hours. 

8.  After  taking  the  article  out  of  the  press  all  inequalities  in 
the  cloth — which  has  now  under  the  influence  of  the  lacquer 
become  harder  than  wood — are  smoothed  down  with  a  knife  or 
with  a  plane. 

9.  Next,  a  coating  like  No.  5  is  applied  with  a  wooden  spatula, 
to  hide  the  texture  of  the  hempen  cloth,  and  the  article  is  again 
put  in  the  press  for  twenty-four  hours. 

10.  Next,  a  coating  is  given  of  one  part  of  powdered  burnt 
clay  and  two  parts  of  branch  lacquer,  applied  with  the  spatula, 
after  which  the  article  is  inclosed  in  the  drying-press  for  twenty- 
four  hours. 

11.  Next,  a  coating  is  given  of  one  part  of  powdered  burnt 
clay  and  two  parts  of  branch  lacquer,  applied  with  the  spatula, 


1 70  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

after  which  the  article  is  inclosed  in  the  drying- press  for  twenty- 
four  hours. 

12.  Next,  a  coating  is  given  of  one  part  of  powdered  burnt 
clay  and  two  parts  of  branch  lacquer,  applied  with  the  spatula, 
after  which  the  article  is  inclosed  in  the  drying-press  for  twenty- 
four  hours. 

13.  Next,  the  article  is  given  a  coating  of  equal  parts  of  pow- 
dered brick  and  burnt  clay,  with  which  is  mixed  one  and  one-half 
parts  of  branch  lacquer,  and  the  drying  process  is  repeated  for 
twenty-four  hours. 

14.  Next,  the  article  is  given  a  coating  of  equal  parts  of  powdered 
brick  and  burnt  clay,  with  which  is  mixed  one  and  one-half  parts  of 
branch  lacquer,  after  which  it  is  set  to  dry  for  at  least  three  days. 

15.  The  surface  is  next  ground  smooth  with  a  fine  hard  rubbing- 
stone. 

1 6.  A  hardening  coat  of  branch  lacquer  is  given  with  a  spatula, 
and  set  to  dry  for  twenty-four  hours. 

17.  A  coat  like  No.  5  is  applied  with  a  spatula,  and  set  to  dry 
for  twenty-four  hours. 

1 8.  When  thoroughly  hardened  the  surface  is  ground  with  a 
fine  hard  rubbing- stone. 

19.  Next,  a  thin  coating  of  branch  lacquer  is  applied  with  a 
spatula,  and  the  article  is  set  to  dry  for  twelve  hours. 

20.  A  coating  of  ordinary  lacquer  is  then  applied  with  a  flat 
brush,  and  the  article  is  set  to  dry  for  twenty-four  hours. 

21.  The  surface  is  then  ground  smooth  with  a  kind  of  char- 
coal having  a  rather  rough  grain;   it  is  made  from  the  Magnolia 
hypoleuca. 

22.  A  thin  coating  of  branch  lacquer  is  given  with  cotton  wool — 
old  wool  being  preferred  because  less  likely  to  leave  hairs  behind 
it — and  rubbed  off  again  with  soft  paper,  after  which  the  article 
is  set  to  dry  for  twelve  hours. 

23.  A  coating  of  black  lacquer  is  then  applied,  and  it  is  set 
to  dry  for  twenty-four  hours. 

24.  The  surface  is  rubbed  smooth  with  very  fine  and  soft 
charcoal. 


CHINESE  AND  JAPANESE  LACQUERS.  171 

25.  A  coating  of  black  lacquer  is  then  applied,  and  it  is  set 
to  dry  for  twenty-four  hours. 

26.  The  surface  is  rubbed  smooth  with  very  fine  and  soft 
charcoal. 

27.  The  surface  is  partly  polished  with  finely  powdered  soft 
charcoal,  applied  with  a  cotton  cloth. 

28.  A  coating  of  black  lacquer  is  then  applied,  and  it  is  set  to 
dry  for  twenty-four  hours. 

29.  The  surface  is  now  polished  with  an  equal  mixture  of 
finely  powdered  burnt  clay  and  calcined  and  powdered  deer's 
horns,  applied  with  a  cotton  cloth  and  a  little  oil. 

30.  A  coating  of  branch  lacquer  is  next  given,  applied  with 
cotton  wool  very  thinly,  and  the  article  is  inclosed  in  the  drying- 
press  for  twelve  hours. 

31.  The  workman  dips  his  finger  in  oil,  and  rubs  a  small 
quantity  of  it  over  the  surface,  which  he  then  polishes  with  deer's- 
horn  ashes,  applied  with  a  cotton  cloth  till  a  bright  surface  is 
obtained. 

32.  A    coating    of    branch    lacquer    is    applied    as    in    No. 
30,  wiped    off    with    soft   paper,   and   set    to   dry   for  twelve 
hours. 

33.  The  oil  is  applied  as  in  No.  31,  and  then  a  final  polish- 
ing with  deer's-horn  ashes,  given  with  the  finger  to  the  surface, 
which  now  assumes  the  most  brilliant  polish  of  which  it  is  sus- 
ceptible. 

For  articles  which  are  liable  to  get  rubbed,  such  as  scabbards, 
these  last  two  processes  are  repeated  seven  or  eight  times,  the 
surface  getting  harder  at  each  repetition. 

In  describing  the  above  processes  the  minimum  time  for 
drying  has  in  each  case  been  given,  but  for  the  first  twenty-five 
processes  the  longer  the  article  is  kept  in  the  press  the  better. 
From  the  twenty-eighth  process  to  the  finish  it  is  better  not  to 
greatly  exceed  the  times  mentioned. 

In  making  articles  ornamented  in  gold  lacquer  the  first  twenty- 
two  processes  are  executed,  and  at  this  stage  the  object  is  ready  to 
receive  the  decoration. 


172  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

Transfer  of  Designs.— The  picture  to  be  transferred  to  the 
article  is  drawn  on  thin  paper,  to  which  a  coating  of  size  made 
of  glue  and  alum  has  been  applied.  The  reverse  is  rubbed  smooth 
with  a  polished  shell  or  pebble,  and  the  outlines  very  lightly 
traced  in  lacquer,  previously  roasted  over  live  charcoal  to  pre- 
vent its  drying,  with  a  fine  brush  made  of  rat's  hair.  The  paper 
is  then  laid,  with  the  lacquer  side  downward,  on  the  article  to  be 
decorated,  and  is  gently  rubbed  with  a  whalebone  spatula  wher- 
ever there  is  any  tracing,  and  on  removing  the  paper  the  impress 
may  very  faintly  be  perceived.  To  bring  it  out  plainly  it  is  rubbed 
over  very  lightly  with  a  piece  of  cotton  wool,  charged  with  pow- 
dered tin  or  the  powder  of  a  hard  white  stone,  which  adheres  to 
the  lacquer.  Japanese  paper  being  peculiarly  tough,  upwards 
of  twenty  impressions  can  be  taken  off  from  one  tracing;  this 
tracing  does  not  dry,  owing  to  the  lacquer  used  for  the  purpose 
having  been  partially  roasted,  and  can  be  wiped  off  at  any  time. 

The  next  process  is  to  trace  out  the  veining  of  the  leaves,  or 
such  lines  to  which  in  the  finished  picture  it  is  desired  to  give  the 
most  prominence,  and  these  lines  are  then  powdered  over  with 
gold-dust  through  a  quill.  The  article  is  then  set  to  dry  for 
twenty-four  hours  in  the  damp  press.  The  outline  is  now  drawn 
carefully  with  a  rat's-hair  brush  over  the  original  tracing  line 
with  a  mixture  of  black  lacquer  and  branch  lacquer.  The  whole 
is  then  filled  in  with  this  mixed  lacquer  applied  with  a  hare's- 
hair  grounding-brush.  Gold-dust  is  scattered  over  the  lac- 
quered portion,  and  the  article  is  set  to  dry  for  twenty-four  hours. 
Another  thin  coating  of  this  mixed  lacquer  is  again  given  to  the 
gold-covered  portions,  and  the  article  set  to  dry  for  twelve  hours. 

Next,  a  coating  of  black  lacquer  is  applied  over  the  whole 
surface  of  the  article,  which  is  set  to  dry  for  at  least  three  days. 
It  is  then  roughly  ground  down  with  coarse  charcoal,  the  surface 
dust  being  constantly  wiped  off  with  a  damp  cloth  till  the  pattern 
begins  to  appear  faintly.  Another  coating  of  black  lacquer  is 
then  given  and  the  article  set  to  dry  for  thirty-six  hours.  It  is 
again  ground  down  with  coarse  charcoal  as  before,  this  time 
until  the  pattern  comes  out  well.  The  ensuing  processes  are  the 


CHINESE  AND   JAPANESE  LACQUERS.  173 

same  as  have  been  described  from  No.  28  to  No.  33  inclusive, 
for  plain  lacquer. 

Another  Method  of  Finishing. — Another  method  consists  in 
first  thoroughly  finishing  the  piece  in  the  manner  first  described ; 
then  a  tracing  is  applied  to  the  surface  in  the  manner  described 
for  gold  lacquering;  the  outline  is  carefully  painted  over  with  a 
fine  brush  of  rat's  hair  and  then  filled  in  with  a  hare's-hair  brush, 
using  branch  lacquer  mixed  with  an  equal  weight  of  bright  red 
oxide  of  iron.  Over  this  surface  gold-dust  is  scattered  with  a 
brush  of  horse's  hair  until  the  lacquer  will  not  absorb  any  more. 
The  article  is  then  set  to  dry  for  twenty-four  hours.  A  thin  coat- 
ing is  next  applied  over  the  gold  of  the  finest  and  most  transparent 
lacquer,  and  set  to  dry  for  twenty-four  hours  at  least.  It  is  then 
most  carefully  smoothed  with  soft  fine  charcoal,  and  finally  pol- 
ished off  with  finely  powdered  burnt  clay  and  a  little  oil  on  the 
point  of  the  finger,  until  the  ornamental  portion  attains  a  fine 
polish.  The  veining  of  leaves  and  the  painting  of  stamens,  etc., 
of  flowers,  or  such  other  fine  work,  is  now  done  with  a  fine  rat's- 
hair  brush  charged  with  branch  lacquer  mixed  with  red  oxide  of 
iron;  for  this  special  use  the  lacquer  has  been  allowed  to  stand, 
after  mixing,  about  six  months,  which  causes  it  to  be  thicker  and 
less  disposed  to  run,  so  that  it  will  make  fine  lines,  and  it  will 
besides  stand  up  more.  Over  this  fine  gold-dust  is  scattered  with 
a  horse's-hair  brush,  as  before,  and  the  article  set  to  dry  for  twelve 
hours.  Some  fine  transparent  lacquer  is  then  applied  to  a  piece 
of  cotton  wool,  and  rubbed  over  the  whole  surface  of  the  box 
or  other  article,  and  wiped  off  again  with  soft  paper.  It  is  set  to 
dry  for  twelve  hours,  after  which  it  is  polished  off  with  deer's- 
horn  ashes  and  a  trifle  of  oil.  If  a  very  fine  surface  is  desired, 
this  last  lacquering  and  polishing  is  repeated. 

Lacquer  on  Metal. — For  lacquering  on  iron  or  copper,  brass 
or  silver,  the  metal  is  polished,  then  given  a  coat  of  black  lacquer, 
and  put  over  a  charcoal  fire  and  the  lacquer  burnt  on  to  the  metal 
until  all  smoke  ceases  to  escape.  The  fire  must  not  be  too  fierce, 
and  the  metal  must  not  be  allowed  to  get  red-hot,  or  the  lacquer 
turns  to  ashes.  After  it  is  baked  quite  hard  the  surface  is  rubbed 


174  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

smooth  with  soft  charcoal ;  these  operations  are  repeated  three  or 
four  times,  until  a  good  foundation  of  lacquer  has  been  obtained. 
The  subsequent  treatment  is  exactly  such  as  has  been  already 
described,  only  that  the  lacquer  may  be  either  dried  in  a  damp 
press  in  the  ordinary  way  or  it  may  be  hardened  by  baking  over 
the  fire. 

When  work  is  required  in  a  hurry  the  workmen  sometimes 
put  a  pan  of  hot  water,  healed  by  a  charcoal  fire,  into  the  press; 
the  steam  thus  generated  dries  in  an  hour  or  two  the  lacquer 
which  would  ordinarily  take  twenty-four  hours.  But  lacquer 
thus  treated  loses  its  strength  and  is  never  very  hard. 

Treatise  by  Dr.  Rein. — Some  time  after  the  publication  of  Mr. 
•Quin's  report,  Dr.  J.  J.  Rein,  professor  of  geography  in  the 
University  of  Bonn,  spent  some  time  in  Japan,  at  the  expense  of 
,the  German  government,  studying  the  industries  of  that  country. 
The  results  of  his  investigations  were  published  in  a  sumptuous 
volume  in  1889;  and  this  book,  called  "Industries  of  Japan," 
contains  the  most  elaborate  and  detailed  account  of  the  art  of 
lacquering  that  has  yet  appeared.  The  book  has  been  trans- 
lated into  English  and  may  be  found  in  almost  any  large  library; 
hence  it  has  not  been  thought  best  to  attempt  to  give  any  com- 
plete review  of  its  contents.  In  general  it  may  be  said  that  it 
agrees  with  Mr.  Quin's  report;  and  the  following  extracts  are 
given  to  supplement  and  complete  the  account  already  tran- 
scribed. These  extracts  are  not  to  be  understood  as  a  continuous 
statement  from  their  author,  but  are  chosen  to  explain  what 
seems  to  the  present  writer  the  most  important  points. 

Raw  Lacquer. — The  raw  lac  is  called  Ki-urushi;  it  must  be 
purified  before  it  can  be  used  at  all.  It  is  first  pressed  through 
cotton  cloth,  and  is  then  called  Ki-sho-mi,  or  purified  raw  lac. 
It  then  contains  from  ten  to  thirty-four  per  cent,  of  water,  which 
can  be  expelled  by  stirring  in  the  sun  or  over  a  slow  fire,  but 
especially  by  a  water-bath.  It  also  contains  1.7  to  3.5  per  cent. 
of  nitrogenous  matter,  apparently  a  proteid ;  and  3  to  6.5  per  cent, 
of  gum,  similar  to  gum  arabic.  It  contains  from  60  to  80  per  cent, 
of  lac-acid  or  Urushi  acid,  which  is  the  characteristic  ingredient. 


CHINESE  AND   JAPANESE  LACQUERS.  175 

Traces  of  oil  are  sometimes  found ;  the  tapster  oils  his  knife 
and  his  spatula  or  metal  spoon  to  prevent  the  lac  from  sticking; 
to  them.  The  lac-acid  is  soluble  in  alcohol,  ether,  chloroform, 
etc. 

The  Ki-sho-mi,  or  purified  raw  lac,  if  deprived  of  water,  is  a 
gray  or  brown,  syrupy  sticky  liquid;  it  will  absorb  water  and  is 
thereby  made  into  a  jelly,  which  when  painted  on  wood  dries 
very  quickly.  Lac  may  be  thinned  by  heat,  but  is  usually  thinned 
by  the  addition  of  camphor.  This  is  pulverized  and  added, 
undissolved,  to  the  lac,  in  which  it  dissolves. 

Lac  dries  best  in  a  damp  atmosphere  at  a  temperature  from 
10°  C.  to  25°  C.  or  at  most  30°  C. 

Lacquer  Dries  by  an  Enzymotic  Ferment. — The  lac-acid  ex- 
tracted by  alcohol  does  not  dry;  it  requires  the  presence  of 
the  proteid  and  water;  and  if  heated  over  60°  C.  (to  a  tem- 
perature which  coagulates  albumen)  it  loses  its  power  to  dry. 
According  to  Korschelt  (Chemistry  of  Japanese  Lacquer,  Trans.. 
Asiatic  Society  of  Japan,  Vol.  XII)  the  proteid  acts  as  a  ferment 
upon  the  lac-acid  and  causes  the  latter  to  oxidize,  which  causes 
it  to  become  hard.  This  oxidized  lac-acid  is  insoluble  in  all 
the  solvents  of  lac-acid,  and  is  not  acted  on  by  either  acids  or 
alkalies. 

Ki-sho-mi  is  ground  for  some  time  in  a  shallow  wooden  tub, 
to  crush  its  grain  and  give  it  a  more  uniform  fluidity.  It  is  then 
pressed  through  cotton  cloth  or  hemp  linen;  it  is  then  called 
Se-shime,  which  is  a  purified,  filtered,  and  evenly  flowing  raw 
lac.  It  is  ready  for  sale  in  this  condition,  but  not  for  use;  it 
must  be  deprived  of  its  water  by  evaporation.  This  is  done  by 
evaporation  in  the  sun,  or  by  moderate  heat  over  a  coal  fire.  The 
Se-shime  is  poured  into  shallow  pans,,  twenty  to  forty  inches  in 
diameter  and  an  inch  or  an  inch  and  a  half  deep,  and  stirred 
constantly  with  a  flat  paddle.  If  the  wooden  pan  is  heated  by 
holding  it  above  a  fire,  the  operation  takes  several  hours;  if 
without  fire,  it  may  take  sixteen  or  eighteen  hours.  After  this  it 
is  again  filtered  through  cloth.  About  twenty  varieties  of  lacquer 
are  made  from  Se-shime ;  some  of  these  are  from  new  lacquer  o£ 


176  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

•choice  quality,  depending  on  the  size  and  vigor  of  the  tree  and 
the  season,  but  most  of  the  differences  are  made  by  admixtures 
of  other  substances,  such  as  gamboge,  vermilion,  and  especially 
.an  oil,  very  much  like  linseed-oil,  made  from  the  seeds  of  a  culti- 
vated annual  plant,  the  Perilla  ocymoides,  a  labiate  plant  which 
is  sown  in  April,  blossoms  about  the  end  of  September  and  is 
ripe  two  weeks  later,  by  the  middle  of  October.  It  is  extensively 
.grown  in  China  and  Japan. 

The  general  rules  to  be  observed  by  the  lacquerer  are  as 
follows : 

1.  Every  coat  must  be  laid  on  evenly  and  then  gone  over 
crosswise  with  the  brush  or  spatula,  first  in  one.  direction  and 
then  afterward  in  the  other. 

2.  No  new  coat  must  be  put  on  before  the  last  one  is  dry. 

3.  It  can  best  be  determined  when  a  smooth  surface  is  dry 
by  the  condensation  of  the  moisture  breathed  upon  it. 

4.  Only  the  groundwork  can  be  dried  in  the  open  air  or  direct 
sunlight,  and  then  only  when  the  coating  contains  very  little  or 
no  lac  admixture. 

5.  The  drying  of  all  genuine  lacquer  coats  must  take  place  in 
the  damp,  unwarmed  amosphere  of  a  chest,  cupboard,  or  chamber. 
In  order  to  secure  this  the  chest  is  laid  on  its  side  and  washed 
with  a  wet  cloth.    Then  the  lacquered  articles  are  put  in,  and 
the  cover,  which  has  been  washed  also,  is  closed.     The  drying 
cupboard  with  shelves  is  treated  in  the  same  way. 

6.  Such  an  arrangement  serves  to  keep  off  draughts  of  air, 
dust,  and  light  during  drying. 

7.  Every  fine,  finishing  lacquer- varnish  before  it  is  laid  on 
must  be  pressed  once  or  twice  through  a  fine  porous  but  strong 
paper,  by  turning  at  both  ends  in  opposite  directions.     Moder- 
ately warmed,  it  flows  more  freely  and  hastens  the  process. 

8.  After  almost  every  new  coating,  according  to  its  nature, 
comes  rubbing  off  with  a  rubbing-  or  polishing-stone,  or  with 
magnolia  charcoal,  or  with  burned  deer's  horn  (in  the  first  two 
cases  of  course  with  the  addition  of  water),  according  as   the 
operation  follows  groundwork  or  a  later  coating. 


CHINESE  AND   JAPANESE  LACQUERS.  177 

9.  The  carefully  lacquered  article  when  finished  must  not  in 
any  way  reveal  the  make  or  material  of  its  framework,  must  be 
free  from  accidental  unevennesses,  cracks,  and  spots,  must  have 
a  mirror-like  surface  and  not  change  in  drying  nor  by  heating 
with  warm  water.  Finally,  when  breathed  upon  the  moisture 
must  disappear  quickly  and  evenly  from  the  outside  toward  the 
centre,  as  on  polished  steel. 

Brilliance  Developed  by  Age. — Professor  Rein  further  de- 
scribes some  of  the  various  methods  employed  in  decorating 
lacquered  articles  with  gold  and  colors;  these  methods  are  more 
elaborate  and  prolonged  than  any  ever  practised  in  America  or 
Europe.  This  is  partly  due,  no  doubt,  to  the  fact  that  some  of  these 
lacquers,  especially  the  finer  and  more  transparent  ones,  although 
they  appear  to  dry  in  a  few  days,  or  weeks  at  most,  do  not  acquire 
their  full  perfection  and  beauty  for  a  long  time ;  from  Father 
D'Incarville  to  the  latest  writer,  all  agree  that  one  or  more  years 
are  required  for  the  complete  development  of  the  brilliance  of 
the  film  after  it  has  been  applied.  The  present  writer  has  two 
friends  who  were  for  some  years  professors  in  the  University  of 
Tokio,  and  who  were  told  and  believe  that  fine  specimens  of  lac- 
quered ware  take  from  twelve  to  twenty  years  in  finishing.  These 
gentlemen  also  say  that  when  at  intervals  it  was  necessary  to  have 
their  desks  varnished,  their  hands  were  poisoned  by  contact  with 
this  freshly  varnished  surface.  Broken  fragments  of  lacquered 
ware  show  a  great  number  of  layers;  and  there  can  be  no 
doubt  that  the  most  valuable  and  essential  secret  of  the  lacquer- 
workers  is  their  unlimited  patience,  which,  with  the  cheapest 
labor  in  the  world  and  the  readiness  on  the  part  of  wealthy 
collectors,  both  native  and  foreign,  to  pay  for  really  fine  lacquered 
articles  sometimes  more  than  their  weight  in  gold,  make  it  possi- 
ble to  get  results  not  attained  by  our  more  hasty  methods. 

Amount  of  Lacquer  Produced. — Both  Mr.  Quin  and  Professor 
Rein  agree  that  the  price  of  raw  lacquer  in  Japan  in  1880  was 
about  sixteen  dollars  a  gallon,  wholesale;  and  from  investiga- 
tions made  by  the  latter  and  from  ofiicial  Japanese  government 
reports  it  appears  that  the  total  annual  product  of  lacquer  in 


178  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

Japan  was  from  8,000  to  13,000  imperial  gallons.  Its  specific 
gravity  is  about  the  same  as  that  of  water.  Quin  says  a  tree 
will  produce  enough  lacquer  to  fill  a  three-ounce  bottle;  Rein 
estimates  an  average  yield  much  smaller,  from  one  to  two 
ounces;  while  W.  Williams,  in  "The  Middle  Kingdom,"  gives 
twenty  pounds  to  a  thousand  trees,  or  only  one-third  of  an 
ounce  to  the  tree.  No  doubt  the  yield  varies  in  different  regions. 
The  trees  are  a  regular  crop,  being  set  out  by  the  farmer  in  plan- 
tations, on  land  otherwise  waste,  and  require  ten  years  to  mature ; 
then  the  owner  sells  the  whole  crop  of  trees — the  "stumpage," 
as  lumbermen  say — to  a  contractor,  who  in  the  course  of  a  single 
summer  destroys  this  ten  years'  growth  for  the  sap  it  will  pro- 
duce ;  and  he  has  the  dead  timber  to  sell  for  firewood ;  after  which 
the  land  is  again  set  out  with  trees  for  another  ten  years'  crop. 
As  an  acre  will  support  a  thousand  or  twelve  hundred  trees,  it 
may  produce  from  four  to  ten  gallons  of  varnish  in  ten  years. 

The  most  noticeable  thing  about  this  matter  is  the  small 
amount  of  the  annual  product.  At  the  time  of  writing  this  (in 
1903)  a  single  American  company  (the  International  Harvester 
Company)  are  using  375,000  to  400,000  gallons  of  varnish  annu- 
ally, or  thirty  times  as  much  varnish  as  the  total  yield  of  lacquer 
in  Japan;  and  this  is  a  very  minute  part  of  the  varnish  used  in 
this  country.  On  the  other  hand,  sixteen  dollars  a  gallon  is 
more  than  any  one  pays  for  any  considerable  amount  of  varnish 
in  America  or  Europe;  it  is  not  likely  that  ten  thousand  gallons 
of  varnish  is  sold  in  America,  Great  Britain,  all  Europe,  and  all 
their  dependencies,  at  half  of  sixteen  dollars  a  gallon,  in  a  year. 

Our  varnishes,  of  all  sorts,  dry  best  in  a  warm,  light,  dry  room; 
but  these  oriental  lacquers  dry  best  in  a  cold,  wet,  dark  closet. 
This  is  an  extraordinary  thing;  it  is  now  universally  believed 
that  lacquer  dries  by  the  agency  of  a  ferment.  It  is  to  be  remem- 
bered that  there  are  two  sorts  of  ferments,  one  which  appears 
to  be  some  sort  of  a  living  organism,  such  as  yeast;  another, 
such  as  diastase,  which  converts  starch  into  sugar,  is  not  an 
organized  ferment,  and  ferments  of  this  sort  are  called  enzymes. 
One  of  these  enzymotic  ferments  is  present  in  this  oriental  lac- 


CHINESE  AND   JAPANESE  LACQUERS.  179 

quer,  and  it  is  through  its  action  that  the  film  is  oxidized  and 
becomes  hard.  Enzymes  are  very  sensitive  to  heat,  whence  it  is 
necessary  to  dry  this  lacquer  at  a  low  temperature  and  in  a  damp 
atmosphere.  Attempts  have  been  made  by  chemists  to  study  the 
ferments  of  this  lacquer,  and  the  surprising  and  interesting  state- 
ment has  been  recently  published  that  its  ash  contains  a  large 
percentage  of  manganese.  This  is  very  singular;  if  a  drying-oil 
was  used  in  the  mixture,  it  is  possible  that  a  manganese  drier 
had  been  added,  but  there  is  nothing  to  warrant  such  an  infer- 
ence, which  was  certainly  not  believed  by  the  investigator. 

In  conclusion,  the  present  writer  wishes  to  disclaim  any 
original  knowledge  of  the  subject  or  wish  to  be  regarded  as  an 
authority.  It  is  said,  on  what  appears  to  be  good  authority, — 
in  fact,  the  reports  come  from  many  sources  and  through  a  long 
time, — that  manila  and  similar  varnish-resins  have  long  been 
imported  into  China;  and  if  we  ever  get  a  complete  knowledge 
of  the  matter  we  shall  very  likely  find  that  oleo-resinous  var- 
nishes, made  from  these  resins  and  tong  and  Perilla  oils,  have 
also  been  long  known.  The  lacquer,  being  at  once  the  most 
valuable  and  the  most  remarkable  of  varnishes,  is  the  only  one 
which  has  attracted  attention;  but  this  is  merely  a  speculation. 


CHAPTER   XV. 

PROTECTION  OF  METALS  AGAINST  CORROSION. 

FROM  early  times  the  use  of  paints  and  varnishes  to  prevent 
the  rusting  of  metals  has  been  known  to  be  of  importance.  Brass 
does  not,  under  ordinary  conditions,  rust  deeply,  but  it  tarnishes 
quickly  and  needs  some  kind  of  a  lacquer  to  preserve  its  surface; 
but  iron  and  steel  are  easily  corroded,  and  the  corrosion  goes  on 
more  rapidly  as  it  progresses.  Metallic  iron  does  not  exist  in 
any  appreciable  quantity  in  nature;  the  principal  ores  of  iron 
are  hematite,  which  is  the  anhydrous  sesquioxide,  and  limonite, 
much  more  abundant  than  the  former.  It  is  evident  from  this 
that  there  must  be  a  great  affinity  between  iron  and  oxygen,  and 
since  most  of  the  ore  contains  a  little  water,  not  as  a  mixture, 
but  in  chemical  union,  it  is  plain  that  the  presence  of  water  is 
favorable  to  this  combination  of  oxygen  and  iron.  This  com- 
bined water  is  so  firmly  united  to  the  oxide  that  it  can  be  driven 
off  only  by  prolonged  heating  to  redness,  but  the  oxygen  is  so 
strongly  bonded  to  the  iron  that  it  is  only  removed  by  heating 
the  ore  to  a  white  heat  in  intimate  contact  with  white-hot  carbon, 
which  has  such  an  intense  attraction  for  the  oxygen  that  it  is  able 
to  take  it  away  from  the  iron  which  is  left  in  a  molten  condition 
from  the  effect  of  the  intense  heat  necessary  for  the  decomposi- 
tion of  the  ore.  Such  being  the  attraction  between  metallic  iron 
and  oxygen,  it  is  not  surprising  that  they  should  readily  com- 
bine, even  at  ordinary  temperatures.  Their  existence  apart  is 
contrary  to  natural  law,  and  sooner  or  later  they  will  get  together 
in  their  natural  union.  All  we  can  hope  to  do  is  to  prolong  their 
separation  as  much  as  possible.  It  is  said  that  iron  will  not 

rust  in  perfectly  dry  air,  but  this  is  not  of  much  practical  impor- 

180 


PROTECTION   OF  METALS   AGAINST  CORROSION.       181 

tance  because  there  is  no  such  thing,  except  as  it  is  chemically 
prepared  and  kept  in  sealed  apparatus  in  a  laboratory.  It  does 
not  rapidly  rust  in  the  comparatively  dry  air  of  a  desert;  but 
nobody  lives  in  the  desert  to  use  it;  yet  these  facts  clearly  show 
that  moisture  is  a  great  help  to  rust. 

Conditions  Favorable  to  Corrosion. — The  air  not  only  con- 
tains moisture,  but  also  a  small  proportion  of  carbonic  acid,  and 
it  has  been  clearly  demonstrated  that  this  also  is  an  important 
aid  to  corrosion.  Since  iron  in  its  various  forms  is  the  most 
useful  of  all  metals,  it  is  naturally  used  in  greatest  abundance  in 
cities,  and  the  air  of  cities  always  contains,  from  the  burning  of 
coal,  an  excessive  amount  of  carbonic  acid  and  an  appreciable 
amount  of  sulphur  in  various  forms,  chiefly  as  sulphurous  and  sul- 
phuric acid,  which  are  intensely  corrosive,  and  on  the  seacoast 
the  air  also  contains  sea- water  spray  floating  in  it,  which  greatly 
increases  its  corrosive  action.  It  is  well  known  that  heat  accel- 
erates chemical  action,  hence  the  hot,  moist,  sulphurous,  and 
strongly  carbonic  gases  ejected  from  a  railway  locomotive,  or 
from  any  other  coal-burning  furnace,  are  most  powerful  as  cor- 
rosive agents,  and  conversely  the  cold  dry  air  of  northern  latitudes, 
away  from  the  seacoast  or  other  large  bodies  of  water,  has  the 
least  action;  in  such  situations,  indeed,  in  the  winter  the  effect 
seems  to  be  so  slight  as  to  be  hardly  worth  considering. 

Such,  in  brief,  are  the  conditions  which  favor  corrosion,  and 
from  their  consideration  it  is  clear  that  what  is  necessary  to  pre- 
vent corrosion  is  some  means  to  prevent  the  access  of  air  and 
moisture.  It  is  attempted  to  do  this  sometimes  by  embedding 
the  metal  in  cement  or  concrete.  This  is  to  be  considered  good 
practice,  because  the  cement  is  not  only  nearly  impermeable,  but 
it  is  also  strongly  alkaline,  and  of  course  the  free  alkali  prevents 
the  access  of  acid  to  the  metal. 

Protection  by  Cement. — It  is,  however,  possible  to  over- 
estimate the  completeness  of  this  protection,  for  it  is  sometimes 
asserted  that  such  cement  or  concrete  is  really  impermeable, 
which  of  course  is  not  the  case.  Even  neat  Portland  cement 
porous,  and  in  fact  there  are  testing-machines  for 


182  TECHNOLOGY   OF  PAINT  AND    VARNISH 

measuring  the  porosity  of  plates  of  cement,  so  it  is  clear  that 
both  air  and  water,  that  is,  gases  and  aqueous  solutions,  may 
circulate,  more  or  less  slowly,  through  it,  and  as  concrete  is  practi- 
cally used  it  contains  numerous  cavities  which,  while  not  affording 
continuous  channels,  appreciably  lessen  its  impermeability. 

Important  engineering  works  are  often  built  of  concrete  rein- 
forced by  steel  wires,  rods,  or  beams,  sometimes  by  riveted  steel 
frames,  but  depending  largely  on  the  strength  and  rigidity  of  the 
cement.  It  is  an  important  matter  to  know  whether  the  steel  in 
such  a  structure  is  indestructible  or  not.  As  to  that  the  writer  of 
this  does  not  propose  to  express  any  decided  opinion;  but  objec- 
tions are  always  in  order,  if  for  no  other  purpose  than  to  suggest 
desirable  precautions.  In  the  first  place,  it  may  be  observed 
that  the  design  of  the  builder  is  to  make  an  artificial  stone.  Either 
this  must  be  monolithic  or  it  must  have  expansion-joints.  If  the 
former,  it  must  be  remembered  that  it  is  difficult  to  make  a  really 
monolithic  structure  of  considerable  magnitude;  for  concrete 
poured  fresh  on  a  surface  of  similar  concrete  which  has  been 
allowed  to  stand  a  day  or  so,  or  sometimes  only  overnight,  does 
not  form  a  strong  bond  to  it,  even  when  the  greatest  care  is  taken, 
and  the  block  thus  formed  will  separate  along  the  surface  where 
the  interruption  in  work  took  place,  if  any  great  stress  be  applied. 

Considerations  Relating  to  Reinforced  Concrete. — To  make 
a  really  monolithic  block  the  work  of  adding  the  concrete  must  be 
continuous,  'and  this  is  difficult  to  insure  on  very  extensive  work 
lasting  perhaps  for  weeks.  The  steel  may  be  so  placed  as  to 
strengthen  these  joints,  but  it  must  not  be  forgotten  that  the 
strength  depends  chiefly  on  the  steel  at  such  places,  and  also  that, 
although  such  a  joint  may  be  water-tight,  it  is  a  place  where 
there  is  a  tendency  for  the  concrete  block  to  crack  from  changes 
of  temperature.  Steel  thus  embedded  can  change  in  temperature 
only  very  slowly,  but  it  does  change  with  the  mass,  and  its  rate  of 
expansion  and  contraction  may  be  slightly  different  from  that 
of  the  concrete. 

It  may  be  conceded  that  if  air  and  moisture  are  kept  from 
the  metal  it  will  not  rust;  but  it  is  hard  to  be  sure  that  water  is 


PROTECTION   OF  METALS  AGAINST  CORROSION.       183 

kept  out  of  such  a  structure,  and  if  the  steel  rusts  it  not  only  loses 
its  strength,  but  exercises  a  most  destructive  action  on  the  sur- 
rounding concrete,  tending  with  immense  force  to  split  it  to 
pieces,  because  of  the  increase  in  bulk  of  the  iron.  If  we  were 
selecting  a  building  stone,  would  we  choose  one  which  was  tra- 
versed in  every  direction  by  streaks  or  long  crystals  of  a  mineral 
very  different  in  chemical  and  electrical  qualities  from  the  matrix  ? 
It  may  be  doubted.  Quarrymen  would  not  regard  such  a  rock 
as  sound,  and  would  expect  to  find  it  split  in  pieces  or  disinte- 
grated by  the  action  of  the  weather.  It  seems  reasonable,  then, 
to  expect  that  great  care  is  necessary,  in  building  such,  structures, 
to  insure  continuity,  and  especially  to  prevent  the  soaking  of 
the  whole  mass  with  water  from  rain  and  melting  snow;  for  con- 
crete often  has  voids  and  porous  places,  and  little  attention  to 
making  its  surface  water-proof  is  usually  given.  Above  all,  pro- 
vision should  always  be  made  for  drainage,  and  this  is  too  often 
neglected ;  the  whole  mass  is  soaked  and  sodden  with  water  which 
lies  there  month  after  month. 

Expansion-joints. — Some  of  these  objections  do  not  apply 
to  blocks  of  reinforced  concrete  put  together  with  expansion- 
joints.  In  these  structures  it  is  clear  that  the  atmospheric  water 
will  have  access  to  the  joints,  and  in  cold  weather  will  by  freezing 
tend  to  injure  them  unless  it  can  be  kept  out  by  some  elastic 
water-proof  packing  or  can  be  perfectly  drained;  perhaps  both 
precautions  are  not  too  much.  It  is  difficult  to  permanently 
close  a  crack  in  concrete,  and  it  may  be  doubted  if  there  has 
yet  been  built  a  large  mass  of  it,  without  expansion-joints,  which 
has  not  cracked.  These  cracks  naturally  lead  to  weak  places 
in  the  interior  and  conduct  water  and  air  to  these  unknown 
and  inaccessible  recesses,  perhaps  to  hasten  the  destruction  of 
the  inclosed  steel  on  which  the  strength  of  the  structure  depends. 

Should  the  steel  in  such  structures  be  painted?  The  objec- 
tion commonly  made  is  that  in  order  to  get  the  utmost  advan- 
tage from  the  use  of  the  steel,  we  must  have  the  concrete  adhere 
perfectly  to  it,  so  that  there  shall  be  no  break  in  continuity  between 
the  cement  and  the  metal,  and  the  latter  shall  be  a  part  of  the 


1 84  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

concrete  in  the  same  sense  that  the  broken  stone  is.  Is  this 
possible?  The  fragments  of  broken  stone  are  of  somewhat 
similar  nature  with  the  cement.  Their  elasticity  and  rate  of 
expansion  is  the  same;  they  exist  in  little  isolated  pieces,  not 
in  long  threads  or  flat  plates,  and  their  rough  surface  and  irregu- 
lar shape  are  perfectly  adapted  to  the  adhesion  of  the  matrix. 
It  is  not  so  with  steel.  It  is  frequently  said  experiment  has 
shown  in  a  testing-machine  that  cement  adheres  to  iron  with  a 
force  equal  to  its  own  cohesion,  and  this  may  be  correct  if  proper 
care  is  taken  to  make  it  a  direct  pull.  But  probably  every  one 
has  seen  cement  part  from  a  steel  surface  without  much  resist- 
ance, even  if  the  surface  was  specially  prepared  for  it.  There  is 
not  much  difficulty  in  rattling  the  dried  cement  off  a  shovel, 
for  instance;  and  it  is  quite  likely  that  in  any  case  where  the 
enormous  elasticity  of  steel  comes  into  play — and  it  is  because 
of  its  strength  and  elasticity  that  it  is  used — the  so-called  bond 
which  exists  between  the  cement  and  the  metal  is  of  very  little 
account.  This  bond  is  sometimes  spoken  of  as  though  it  were 
something  mysterious  and  sacred,  but  it  may  be  doubted  if  cement 
sticks  to  iron  in  any  different  way  from  what  anything  else  does 
or  from  what  cement  sticks  to  anything  else.  A  definition  of 
this  bond  would  tend  to  a  clearer  conception  of  the  whole  matter, 
and  it  might  then  be  found  that  an  elastic  and  water-proof  film 
between  the  metal  and  the  cement  which  would  lend  itself  a 
little  to  the  differences  in  expansion  was  a  source  of  strength 
and  permanence  rather  than  weakness.  A  subject  like  this  is 
too  important  and  too  intricate  to  be  approached  with  a  feeling 
of  prejudice  and  a  determination  to  settle  the  matter  ex  cathedra. 
We  have  not  yet  got  to  the  last  word  about  reinforced  concrete; 
it  is  very  true  that  time  and  use  are  the  final  test,  and  that  some 
of  the  earlier  structures  are  still  in  good  condition,  but  the  earlier 
structures  were  built  by  men  who  were  in  some  sense  inventors 
and  experimenters,  and  the  work  of  an  enthusiast  is  likely  to 
be  much  more  carefully  done  than  that  of  a  man  who  works  by 
a  formula. 

Asphaltic    Cement. — A   really    impermeable    cement    is    one 


PROTECTION   OF  METALS  AGAINST  CORROSION.       185 

made  of  asphaltum  applied  in  a  melted  condition;  when  of  suit- 
able composition  and  sufficient  thickness  this  seems  to  be  as 
nearly  perfect  a  protection  as  anything  which  has  been  devised. 
Coal-tar  pitch,  which  resembles  asphaltum  in  appearance,  is 
usually  an  acid  substance  and  should  not  be  used  for  these  pur- 
poses, and  it  is  not  to  be  forgotten  that  asphaltum  is  mixed  with 
all  sorts  of  things,  some  of  which  are  not  injurious  if  not  used 
in  too  great  quantity,  but  the  best  of  which  usually  so  dilute  the 
asphalt,  which  is  the  real  cementing  material,  as  to  lessen  its 
permanence. 

To  be  of  any  value  as  a  cement  asphaltum  must  be  tough 
and  somewhat  flexible,  a  quality  usually  obtained  by  using  a 
naturally  soft  asphalt,  or  by  tempering  a  harder  asphalt  with  a 
heavy  mineral  oil;  in  either  case  the  elastic  or  softening  ingre- 
dient tends  to  be  removed  by  atmospheric  action,  and  still  more 
by  the  effect  of  the  weather  or  of  water,  and  it  is  necessary  to 
have  a  considerable  thickness  of  cement  over  the  metal,  not 
less  than  an  inch,  and  better  two  or  more  inches,  when  efficient 
protection  may  be  reasonably  expected.  Such  an  asphaltic 
cement  is  not  only  tough  and  flexible,  but  it  is  also  viscous.  It 
will,  especially  in  warm  weather,  flow  slowly.  This  naturally 
prevents  its  use  in  places  where  it  can  run  off.  It  is  used  for 
covering  rail  way- bridge  floors,  and  when  used  in  sufficient  quan- 
tity and  with  a  reasonable  appreciation  of  its  properties  satis- 
factory results  have  been  attained.  An  important  use  for  ma- 
terial of  this  sort  is  in  coating  water-pipe,  a  subject  which  will 
be  treated  as  a  separate  topic.  These  methods  deserve  fuller 
treatment,  especially  the  use  of  Portland  cement,  but  at  the 
present  time  there  is  but  little  accurate  knowledge  and  especially 
hardly  any  which  has  been  tabulated  or  otherwise  made  accessible 
on  the  subject  of  hydraulic  cement  for  such  use,  and  the  making 
of  serviceable  mixtures  of  asphalt  is  in  the  hands  of  the  great 
asphalt  paving  companies,  who  do  not  make  it  known,  so  that 
this  must  be  left  for  some  better-informed  writer  in  the  future. 

Thinness  of  Films. — We  come,  then,  to  the  problem  of  pro- 
tecting metal  from  corrosion  by  the  use  of  films  of  varnish  and 


186  TECHNOLOGY   OF  PAIN1    AND    VARNISH. 

paint.  The  statement  of  the  problem  involves  naming  its  great- 
est defect,  which  is  that  films  are  depended  on  for  more  or  less 
permanent  protection,  and  these  films  are  only  one  or  two  thou- 
sandths of  an  inch  in  thickness.  They  are,  therefore,  easily 
scraped  off  or  removed  by  any  sort  of  abrasion.  They  are  not 
very  hard  and  are  easily  punctured,  and  if  they  are  at  all  porous 
the  pores,  which  will  naturally  be  at  an  angle  to  the  surface  of 
the  film,  will  extend  through  it  because  the  distance  is  so  little. 
If  the  matter  is  fairly  considered,  it  seems  almost  preposterous 
to  apply  a  film  one  or  two  thousandths  of  an  inch  thick  to  protect 
a  steel  plate  or  beam  an  inch  or  more  in  thickness  in  a  situation 
where  the  uncoated  metal  would  be  destroyed  in  a  short  time, 
yet  this  is  what  is  constantly  demanded,  and  it  is  also  asked  that 
this  material  should  be  such  as  may  be  applied  by  unskilled 
labor  and  to  any  kind  of  a  surface.  It  is  a  wonder  that  any 
favorable  results  are  reached,  yet  they  must  be  or  the  varnishes 
and  paints  would  not  be  used. 

Paint  is  Engineering  Material. — Protective  coatings,  as  applied 
to  structures  designed  by  engineers,  are  engineering  materials, 
just  as  much  as  are  the  plates  and  beams  to  which  they  are  applied. 
When  an  engineer  designs  a  structure,  he  makes  it  usually  from 
three  to  five  times  as  heavy  as  the  load  actually  requires,  "for 
safety";  really  this  factor  of  safety  is  so  large  chiefly  to  provide 
for  future  deterioration,  and  a  part  of  this  excess  of  metal  is  added 
to  secure  the  rest  of  it  against  rust,  which  is  exactly  what  the  paint 
is  used  for;  hence  the  latter  is  fully  as  much  engineering  material 
as  the  steel  which  it  covers,  and  deserves  just  as  careful  and  serious 
consideration  from  the  engineer — which  it  seldom  gets.  Part  of 
the  indifference  to  the  subject  is  due  to  the  fact  that  the  engineer 
feels  that  he  is  rather  ignorant  of  the  matter  and  concentrates 
his  interest  on  steel,  of  which  he  thinks  he  knows  a  great  deal, 
though  it  may  be  suspected  that  the  chemists  in  the  steel- works 
have  their  own  doubts  about  even  that;  but  at  any  rate  he  has 
books  of  tables  of  figures  relating  to  steel,  and  these  are  a  source 
of  satisfaction.  The  imaginative,  the  mathematical,  the  construc- 
tive part  of  engineering  is  and  must  always  be  a  delight  to  the 


PROTECTION  OF  METALS  AGAINST  CORROSION.       187 

mind  of  the  engineer,  and  is  essentially  different  from  that  part 
which  has  to  do  with  the  qualities  of  materials,  which  are  best 
understood,  and  even  then  only  imperfectly  known,  by  the  experts 
who  make  a  business  of  their  manufacture. 

Protective  Coatings  not  Necessarily  Decorative.  —  It  has 
already  been  said  that  varnish  and  paint  are  used  both  for  decora- 
tive effect  and  for  protection  of  the  underlying  materials,  and  as 
the  decorative  effect  is  the  more  conspicuous,  most  people  regard 
that  as  the  primary  quality;  and  when  we  speak  of  protective 
coatings  the  idea  of  decorative  effect  underlies,  in  their  minds, 
the  whole  matter,  perhaps  unconsciously.  By  the  very  term 
used  it  is,  however,  eliminated.  The  decorative  effect  has  abso- 
lutely nothing  to  do  with  the  subject.  Fortunately  this  con- 
dition, that  no  attention  whatever  shall  be  paid  to  decorative 
effect,  can  in  most  cases  be  enforced,  because  such  effect  may  be 
reached  by  decorative  painting  over  the  protective  coating,  not 
only  without  injury,  but  in  most  cases  with  positive  benefit  to 
the  latter.  This  is  an  important  consideration,  for  it  enables  us 
to  use  materials  which  are  quite  unsuited  for  decorative  use. 
For  example,  a  paint  or  varnish  as  commonly  used  must  dry 
" dust-free,"  i.e.,  so  that  dust  will  not  stick  to  it,  in  about  twenty- 
four  hours,  or  less,  because  every  hour  adds  to  the  danger  that 
the  beauty  of  the  surface  will  be  destroyed  or  injured  by  the 
adhesion  of  dirt,  insects,  etc.,  and  this  quality  of  quick  drying  is 
almost  always  obtained  by  the  excessive  use  of  driers  which,  as 
has  been  already  explained,  greatly  lessens  the  durability  of  the 
compound,  or  else  by  the  use  of  too  large  a  proportion  of  resin- 
ous matters,  which  makes  a  brittle  coating  which  cracks  with 
changes  of  temperature,  or  too  much  volatile  solvent  is  used, 
which  diminishes  the  proportion  of  cementing  material  and  pro- 
duces a  film  which  is  lacking  in  coherence.  If,  on  the  other 
hand,  we  may  leave  out  of  account  the  looks  of  the  paint  or 
varnish,  it  is  clear  that  we  are  at  liberty  to  use  anything  which 
will  add  durability  and  impermeability  to  the  film,  which,  in 
most  cases,  may  be  allowed  a  long  time  to  dry  and  may  have  a 
comparatively  rough  and  wrinkled  surface.  Thus,  the  members 


1 88  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

of  a  bridge  are  usually  made  up  several  weeks  before  erection, 
and  a  first  coat  has  all  this  time  to  dry  and  harden;  then  it  is 
painted  after  erection,  and  in  most  cases  this  coat  may  have  all 
the  time  necessary.  Probably  in  most  cases  the  next  coat  will 
not  be  applied  for  some  months,  and  in  any  subsequent  painting 
the  use  of  a  slow-drying  paint  does  not  interfere  with  the  use 
of  the  structure.  Of  course  there  are  considerations  which  pre- 
vent the  use  of  non-drying  or  too-slow-drying  materials:  they 
are  liable  to  be  rubbed  off  or  even  removed  by  the  action  of  the 
weather;  it  is  desirable  to  have  a  paint  or  varnish  which  sets 
within  a  reasonable  time,  say  a  day  or  two,  but  it  may  be  allowed 
to  dry  slowly  after  that,  taking  up  its  last  portions  of  oxygen 
only  after  a  long  period,  and  it  is  films  of  this  nature,  which  show 
a  continually  increasing  reluctance  to  oxidize,  which  have  the 
greatest  permanence.  To  exhibit  a  very  smooth  surface  a  paint 
or  varnish  must  contain  a  considerable  proportion  of  resinous 
matter;  and  while  a  certain  amount  is  highly  desirable,  because 
it  acts  as  a  flux  and  prevents  the  formation  of  pores,  a  quantity 
sufficient  to  give  a  hard  and  very  lustrous  surface  causes  a  lack 
of  elasticity  which  may  be  the  occasion  of  cracks  in  the  coating, 
but  a  film  intended  only  to  protect  against  corrosion  may  have 
exactly  the  most  desirable  ratio  of  ingredients.  Decorative  paints 
must  be  made  with  certain  pigments,  and  sometimes  these  are  the 
cause  of  deterioration;  but  an  injurious  pigment  should  be  excluded 
from  protective  coatings,  which  should  contain  only  the  best  and 
most  suitable  compounds  for  the  purposes  for  which  they  are 
made. 

The  preparation  of  the  surface  to  which  the  protective  coat- 
ing is  to  be  applied  is  a  subject  the  consideration  of  which  natu- 
rally precedes  that  of  the  material  itself  and  of  the  method  of  its 
application.  A  great  many  years  of  experience  and  observation, 
and  of  consultation  with  painters  and  with  engineers,  have  con- 
vinced the  writer  that  paint  and  varnish  adhere  to  a  metal  sur- 
face in  the  same  way  that  other  things  do,  and  that  the  same 
conditions  which  favorably  influence  the  adhesion  of  other  coat- 
ings are  desirable  in  the  use  of  these  substances ;  also  that,  making 


PROTECTION   OF  METALS  AGAINST  CORROSION.       189 

due  allowance  for  the  impermeability  of  a  metallic  surface  as 
compared  with  a  wooden  one,  the  same  principles  which  govern 
their  application  to  all  other  surfaces  apply  to  their  use  on  iron 
and  steel.  Such  statements  as  the  foregoing  will  not  probably 
appear  to  the  disinterested  and  speculative  reader  to  be  unreason- 
able, much  less  revolutionary  and  inimical  to  all  industrial  prog- 
ress, and  he  cannot  fail  to  be  interested  in  knowing  that  not  only 
the  ordinary  contractor  but  the  great  steel  companies  (who  natu- 
rally ought  to  be  interested  in  the  permanence  of  their  products) 
regard  an  engineer  who  tries  to  adapt  these  maxims  to  practical 
work  as  a  visionary  theorist,  to  be  humored  when  necessary  and 
evaded  if  possible,  while  the  paint  or  varnish  manufacturer  who 
promulgates  such  propositions  is  a  dangerous  crank,  about  as  use- 
ful to  society  as  an  anarchist.  "  That, "  said  the  manager  of  one  of 
the  great  bridge  companies,  "is  a  good  paint,  but  it  always  makes, 
me  laugh  when  I  see  a  barrel  of  it;  observe  the  notice  on  the 
barrel-head:  'Do  not  thin  this  with  anything.'  Well,  we  thin  it: 
just  the  same.  Oh,  we  have  to  thin  it  a  little,  you  know,  or  we 
couldn't  put  on  two  coats;  with  the  same  brush,  you  know;  one 
coat  going  this  way" — with  a  sweep  of  the  arm  indicating  a  free 
and  powerful  artistic  treatment — "and  the  other" — with  a. 
return  sweep — "going  this  way.  Why,"  plaintively,  "do  you. 
suppose  we  wish  this  steel  to  last  forever?"  "I  suppose,"  said  I 
sadly,  "you  consider  me  an  enemy  of  the  human  race."  "Oh, 
no,  you're  a  good  fellow,  but  you  are  an  enemy  of  the  steel  men. " 
Apply  Paint  to  a  Clean  Surface. — The  most  important  con- 
dition affecting  the  adhesion  of  any  coating  to  any  metal  is  that 
it  should  be  applied  to  a  clean  metallic  surface.  If  the  surface 
is  covered  with  dirt  or  grease,  the  coating  does  not  come  in  con- 
tact with  the  metal  and  so  does  not  adhere  to  it ;  and  if  the  dirt 
comes  off,  the  coating  comes  with  it.  It  might  be  supposed  that 
grease  would  be  absorbed  by  the  paint  or  varnish,  but  the  coating 
of  grease  or  oil  does  not  very  readily  mix  with  these.  If  it  were 
desired  to  mix  such  things,  it  would  ordinarily  be  thought  neces- 
sary to  agitate  them  thoroughly  together.  But  an  important 
consideration  is  that  the  grease  is  always  mixed  with  and  covered 


TECHNOLOGY   OF  PAINT  AND    VARNISH. 

by  an  adherent  film  of  dirt  which  interferes  with  the  action  of 
the  paint  or  varnish  upon  it,  which  consequently  makes  a  film 
on  a  loose,  greasy  foundation.  Further,  the  oil  or  grease  is  usually 
a  mineral  oil,  sometimes  mixed  with  rosin  or  rosin-oil,  and  if 
mixed  with  the  regular  coating  will  destroy  the  characteristic  and 
valuable  qualities  of  the  latter.  Iron  and  steel  beams  and  the 
like  should  not  be  laid  on  the  ground,  but  on  skids  or  trestles. 
They  are  heavy  and  press  into  the  earth,  which  adheres  to  them ; 
in  wet  weather  they  become  covered  with  mud,  which  the  con- 
tractor strenuously  objects  to  removing  before  painting.  "Do 
you  expect  me  to  clean  this  iron  with  a  tooth-brush?"  was  the 
angry  protest  of  the  manager  and  one  of  the  principal  stock- 
holders of  one  of  the  largest  construction  companies  in  New 
York,  when  the  engineer  was  urging  him  to  wash  the  mud  off  the 
beams  which  had  been  lying  in  the  street,  although  his  contract 
specified  much  more  thorough  cleaning  than  he  was  asked  to  do. 
Sometime  when  steel  becomes  more  costly  than  it  is  now,  or 
opinion  on  these  matters  becomes  more  enlightened,  it  will  be 
kept  under  shelter  until  the  time  comes  for  its  erection. 

Mill-scale. — But  oil  and  dirt  are  not  the  only  things  found  on 
steel.  All  structural  metal  as  it  comes  from  the  mill  is  covered 
with  mill-scale,  which  is  the  black  oxide  of  iron  resulting  from 
the  action  of  air  on  the  hot  metal.  Frequently  this  scale  is  in 
several  layers;  sometimes  these  stick  together  rather  firmly, 
sometimes  the  outer  layers  separate  readily  from  those  beneath. 
Steel  plates  are  often  coated  with  a  thin  blue  or  iridescent  mill- 
scale,  which  immediately  overlays  the  unoxidized  metal,  to  which 
it  sometimes  adheres  with  great  tenacity.  This  is  the  anhydrous 
sesquioxide,  and  is  exactly  similar  in  appearance  and  compo- 
sition to  the  beautiful  iridescent  specimens  of  hematite  ore  which 
may  be  seen  in  any  mineralogical  collection.  This  is  an  extremely 
refractory  substance,  insoluble  in  acid,  and  might  be  thought  to 
be  a  sufficient  protective  coating  in  itself,  but  it  is  hard  and  not 
very  elastic,  and  its  rate  of  expansion  differs  from  that  of  the 
metal,  so  that  it  soon  becomes  a  network  of  cracks,  which  allow 
water  to  reach  the  underlying  metal,  which  then  rusts  and  the 


PROTECTION   OF  METALS  AGAINST  CORROSION.       191 

rust  creeps  under  the  little  patches  of  scale  and  they  are  thrown 
off.  This  may  be  easily  seen  by  immersing  a  piece  of  such  iron 
in  acid,  which  can  reach  the  metal  only  through  the  cracks  in  the 
scale.  Scale  which  is  of  a  more  pulverulent  character  offers 
little  or  no  resistance  to  atmospheric  agencies,  but  it  does  not 
scale  off  easily  unless  in  deep  layers.  .It  is  dangerous  to  leave 
such  oxide  in  contact  with  the  iron,  for  it  absorbs  and  holds  in 
contact  with  the  metal  the  moisture  and  acids  in  the  air  and  in 
various  ways  acts  to  induce  further  and  deeper  oxidation.  It 
might  be  thought  that  saturating  the  oxide  with  oil  would  prevent 
any  further  change,  but  this  idea,  though  it  crops  up  from  time 
to  time  and  is  the  base  of  many  a  humbug  in  the  paint  line,  is  not 
in  the  least  supported  by  practical  experience.  I  do  not  mean 
to  say  that  a  surface  covered  with  mill- scale,  or  even  with  ordinary 
rust,  may  not  be  benefited  by  a  good  paint  or  varnish.  These 
coatings  will  undoubtedly  retard  the  further  action  of  rust,  but 
do  not  prevent  it.  More  than  a  hundred  years  ago,  Smeaton, 
one  of  the  greatest  engineers  of  his  time,  said  he  "had  observed 
that  when  iron  once  gets  rust,  so  as  to  form  a  scale,  whatever  coat 
of  paint  or  varnish  is  put  on  over  this,  the  rust  will  go  on  pro- 
gressively under  the  paint."  The  following  century  of  obser- 
vation has  made  no  change  in  this  remark,  which  is  only  confirmed 
by  longer  experience. 

Rust  must  be  Removed. — Iron  and  steel  are  of  a  grayish- white 
color.  When  it  is  desired  to  coat  articles  of  this  metal  with 
porcelain  or  a  vitreous  enamel  the  workman  finds  it  absolutely 
necessary  to  have  the  surface  show  this  color  of  the  pure  metal 
in  all  its  parts,  for  if  there  is  any  scale  or  rust  on  the  surface, 
even  in  minute  spots,  the  enamel  will  chip  off  at  those  places. 
This  clean  surface  he  gets  by  clearing  off  the  scale  with  acid,  in  a 
manner  to  be  described  later,  or  by  the  use  of  the  sand-blast,  or 
sometimes  by  scraping  and  polishing  the  metal.  At  all  events, 
the  enamel  is  applied  to  the  metal  and  never  to  an  intermediate 
coating.  The  electroplater,  who  deposits  another  metal,  such  as 
copper  or  nickel,  on  iron,  is  equally  thorough.  The  bicycle- 
maker,  who  covers  his  frames  with  a  japan  enamel,  cleans  them 


TECHNOLOGY   OF  PAINT  AND    VARNISH, 

in  the  most  perfect  manner  on  an  emery- belt,  after  which  they  must 
not  be  touched  even  with  the  finger  until  the  enamel  is  applied. 
In  making  tin-plate,  the  iron  plates  are  cleaned  by  acid  and  go 
•direct  from  the  acid-bath  to  the  pot  of  melted  tin,  for  otherwise 
no  adhesion  will  take  place.  Galvanizing,  or  plating  with  zinc, 
is  done  in  the  same  way. 

No  Coating  will  Stand  over  Oxide. — Excepting  the  painter, 
every  one  who  applies  protective  coatings  to  iron  or  steel  insists, 
as  a  matter  which  will  not  admit  of  discussion,  on  the  absolute 
and  fundamental  necessity  of  removing  not  merely  all  loose  scale 
and  dirt,  but  absolutely  all  scale  and  all  oxide,  so  as  to  apply  the 
coating  to  the  pure  metallic  surface.  Otherwise  it  has  been  found 
that,  sooner  or  later,  the  oxide  will  separate  from  the  metal  surface 
and  of  course  the  superimposed  coating  has  to  come  off.  This 
is  what  I  mean  when  I  say  the  conditions  which  favorably  influence 
the  adhesion  of  other  coatings  are  desirable  for  the  application 
of  varnish  and  paint,  and  it  is  this  idea  of  having  an  absolutely 
clean  metal  surface  on  which  to  apply  these  coatings  which  seems 
the  extravagant  dream  of  a  doctrinaire  to  the  ordinary  contractor, 
who  will  tell  you  that  paint  forms  a  continuous,  film  and  keeps 
out  the  air  and  water,  so  that  there  can  be  nothing  to  cause  the 
closely  adherent  oxide  to  separate  from  the  metal.  It  is  a  suffi- 
ciently complete  answer  to  this  argument  to  repeat  that  universal 
experience  shows  that  nothing  can  prevent  it  in  practice.  If  it 
cannot  be  done  with  such  a  perfect  coating  as  electroplate  or  a 
vitreous  enamel,  nor  with  a  coating  which  in  some  respects  is 
even  more  remarkable,  namely,  one  of  baking- japan,  which  more 
nearly  resembles  a  varnish  or  paint,  it  is  idle  to  expect  it  with 
these  latter,  which  are  in  their  nature  somewhat  porous  and 
with  which  we  have  to  obtain  protection  by  putting  one  coat  on 
•over  another,  trusting  to  the  successive  coats  to  fill  up  the  pores 
.and  imperfections  of  those  beneath.  There  is  no  doubt  in  my 
mind  that  the  right  way  to  prepare  a  steel  or  iron  surface  for 
painting  is  to  clean  it  so  that  the  gray  color  of  the  metallic  iron 
will  be  everywhere  seen.  This  may  be  done  in  some  cases  by 
scraping,  in  some  by  pickling  in  acid,  in  others  by  the  sand-blast, 


PROTECTION  OF  METALS  AGAINST  CORROSION.       IQ3 

but  in  all  the  cost  will  be  considerably  more  than  is  now  com- 
mon, because  more  work  is  done  and  a  better  result  achieved. 
Money  judiciously  spent  to  get  a  good  surface  is  wisely  invested; 
no  one  doubts  that  it  is  if  really  high-class  work  is  in  question. 
No  doubt  there  is  a  great  deal  of  work  of  a  more  or  less  tem- 
porary nature  where  the  cost  of  such  high-class  treatment  is  not 
justified,  but  there  is  no  place  where  a  protective  coating  is  called 
for  where  it  is  not  worth  while  to  make  some  effort  to  secure  a 
fairly  good  surface,  free  from  mud  and  dirt  and  loose  scale,  for 
the  varnish  or  paint.  We  may  also  consider  the  practice  of  the 
painter  who  works  on  wood.  No  one  ever  thinks  of  painting 
on  wet  wood;  the  paint  will  not  stick;  if  it  does  not  immediately 
come  off,  it  will  subsequently  blister;  and  even  in  such  rough  work 
as  exterior  house-painting  the  painter  removes  all  loose  dirt, 
old  paint,  etc.,  by  scraping  and  brushing,  as  a  preliminary;  in 
fine  work,  such  as  repainting  a  carriage,  the  old  paint  is  removed 
by  scraping  or  burning  off,  and  the  surface  made  clean  and 
smooth  and  properly  prepared  by  special  fillers,  so  that  the  paint 
or  varnish  may  go  on  in  a  coat  of  uniform  thickness  to  a  surface 
for  which  it  has  a  natural  affinity.  Thus  it  will  be  seen  in  all 
other  painting  the  proper  condition  of  the  surface  is  a  subject 
of  practical  consideration,  and  its  preparation  a  matter  of  serious 
care.  This  also  indicates  that  like  precautions  should  be  taken 
with  steel,  in  fact  greater,  because  steel  is  in  most  situations 
more  perishable  than  wood. 

Why  Steel  is  not  Fairly  Treated. — The  curious  reader  will 
perhaps  wonder  why  it  is  that  difficulty  should  be  found  in  hav- 
ing steel  properly  cleaned  and  painted.  Primarily  the  trouble 
is  with  the  engineers  who  design  and  direct  the  work.  If  they, 
as  a  class,  felt  the  importance  of  the  matter  and  were  always 
as  strenuous  about  it  as  they  are  about  the  mechanical  details, 
and  made  it  a  rule  to  include  in  their  estimates  a  reasonable 
amount  for  having  such  work  properly  done,  there  would  then 
exist  a  better  general  practice,  and  if  the  average  were  higher 
it  would  be  comparatively  easy  to  get  really  high-class  work 
done.  Structural  steelwork  goes  mainly  into  two  classes,  bridges 


194  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

and  the  framework  of  buildings.  The  building  with  a  steel 
framework  is  primarily  designed  by  an  architect  who,  while 
not  without  engineering  knowledge,  hands  over  the  details  of 
construction  to  an  engineer.  The  chief  architect  himself  is 
mainly  concerned  with  the  design  of  a  building  suitable  in  its 
general  and  detailed  arrangements  for  the  purposes  of  the  owner 
and  in  having  its  artistic  features  and  its  ornamental  details  as 
agreeable  as  possible,  and  strict  regard  must  and  should  be  had 
for  economy  of  construction.  Usually  a  sum  to  be  expended  is 
fixed  upon  at  first ,  and  the  common  experience  is  that  for  various 
reasons  the  estimated  cost  is  finally  exceeded.  The  architect 
usually  does  not  know  or  claim  to  know  much  about  protective 
painting.  The  engineer  is  sometimes  directly  and  sometimes 
indirectly  in  his  employ  and  receives  his  directions.  He  is, 
therefore,  not  finally  responsible  and,  not  being  oversupplied 
with  subordinates,  does  not  feel  like  assuming  unusual  authority 
or  cares.  The  metal  framework  is  to  be  eventually  covered  from 
sight,  and  as  it  is  inclosed  it  is  not  as  likely  to  rust  as  though 
exposed;  and  above  all,  the  current  practice  of  architectural 
engineers  is  to  be  indifferent  about  painting,  so  that,  with  lack 
of  responsibility,  lack  of  authority,  disbelief  in  the  vital  impor- 
tance of  the  subject  and  accordance  with  current  practice,  the 
engineer  leaves  the  painting  largely  to  the  contractor,  and  it  is 
unreasonable  to  expect  the  latter  to  spend  money  for  material 
or  labor  which  are  not  called  for.  Further,  it  is  commonly  the 
case  that  when  the  money  to  build  with  is  ready  it  is  important 
to  get  the  building  done  as  soon  as  possible.  So  the  steel  is 
rushed  through  the  shops  as  rapidly  as  may  be;  when  it  is  de- 
livered it  is  in  the  street  in  front  of  the  building,  and  the  building 
permit  is  limited;  hence  it  cannot  stay  there,  but  must  be  put  in 
place  at  once,  and  then  the  masons  are  waiting  and  there  is  no 
time  to  paint. 

Stone  does  not  Rust. —  The  engineer  consoles  himself  by 
thinking  that  he  has  done  the  best  he  can  and  as  well  as  other 
people  do;  and  in  fact  the  engineer  who  holds  that  life  is  too 
short  to  be  studying  this  paint  question  and  that  there  is  no  oppor- 


PROTECTION   OF  METALS  AGAINST  CORROSION.       195 

tunity  in  the  construction  and  erection  of  metal-work  for  its 
proper  application  may  feel  confident  that  he  has  good  com- 
pany and  plenty  of  it;  but  his  attention  may  be  called  to  the 
fact  that  some  of  our  best  and  most  important  railroads  have 
gone  back  to  the  construction  of  enormously  expensive  stone 
bridges  simply  because  stone  is  reliable,  while  steel,  as  now 
treated,  is  not. 

As  to  bridge  construction,  it  is  common  practice  for  one 
department,  whether  of  a  private  or  public  corporation,  to  design 
and  erect  a  bridge,  and  then  turn  it  over  to  another  department 
for  maintenance,  and  the  bridge  engineer  holds  that  painting 
is  a  part  of  maintenance,  and  that  he  may  build  the  bridge  with- 
out regard  to  paint  and  let  the  engineer  of  maintenance  paint  it 
as  often  as  he  likes.  Hence  it  is  of  no  use  to  try  to  interest  such 
a  bridge  engineer  in  materials  or  methods  of  painting.  A  little 
consideration  will  show  that  this  position  is  untenable  if,  as 
has  been  claimed,  paint  is  engineering  material.  The  construct- 
ing engineer  might  as  well  say  that,  as  defective  rivets  and  bolts 
have  to  be  renewed  by  the  department  of  maintenance,  it  is  of 
no  importance  to  him  what  is  the  quality  of  material  or  work- 
manship employed  in  riveting.  The  place  to  begin  painting 
is  on  the  metal,  and  the  first  coat  is  of  more  importance  than 
any  subsequent  one.  My  own  belief  is  that  a  bridge  should 
never,  except  for  decorative  effect,  be  repainted  throughout; 
it  should  be  well  and  properly  painted  when  built,  and  any  spots 
which  are  defective  should  be  repainted  from  time  to  time,  pre- 
cisely as  all  other  repairs  are  managed;  no  one  would  think 
of  conducting  other  repairs  in  any  other  way,  and  the  paint  is 
just  as  much  a  part  of  the  bridge  as  any  other  material  and  should 
be  treated  in  the  same  way;  and  I  am  glad  to  be  able  to  say  that 
some  of  the  best-maintained  railways  have  adopted  this  practice. 

Scraping. — This  doctrine  that  rust  and  scale  should  be  re- 
moved as  much  as  possible  before  painting  is,  of  course,  no  new 
thing;  and  the  earliest  method,  and  one  which  will  always  be 
in  many  cases  the  only  one  available,  was  to  clean  the  surface 
by  scraping.  The  most  common  scraper  is  one  made  by  grind- 


196  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

ing  the  end  of  a  large  mill-file,  which  makes  an  efficient  tool. 
But  there  are  many  places  which  cannot  be  reached  with  such 
an  instrument,  and  now  the  workman  is  provided  with  sets  of 
scrapers  of  different  widths,  and  with  a  hammer  and  chisel,  which 
are  sometimes  necessary.  The  common  straight  scraper  is 
operated  by  pushing,  but  others  are  made  with  the  scraping  end 
bent  at  a  right  angle  to  the  shank,  which  are  pulled,  like  a  hoe, 
toward  the  operator.  These  are  also  made  in  different  widths. 
The  edge  of  a  scraper  is  naturally  straight  like  that  of  a  chisel, 
the  workman  is  also  sometimes  provided  with  one  or  two 
ones  having  the  edge  serrated,  like  the  teeth  of  a  saw  or  of 
a  serrated  ice-chisel,  and  these  are  useful  for  breaking  up  scale 
so  that  it  may  more  easily  be  removed. 

Wire-brushing. — After  the  scraping  it  is  customary  to  go 
over  the  surface  with  a  wire  brush,  which  leaves  a  good  surface, 
but  the  brush  alone  is  not  an  efficient  instrument.  In  my  own 
laboratory  there  is  a  rotary  wire  brush  driven  by  power  with  a 
peripheral  speed  of  about  five  thousand  feet  per  minute.  A 
•suitable  table  is  arranged  so  that  the  piece  of  metal  to  be  cleaned 
may  be  mechanically  held  at  the  right  place  and  the  brushing 
may  be  continued  as  long  as  the  operator  desires.  This  is  prob- 
ably the  most  favorable  condition  for  the  use  of  a  wire  brush,  but  it 
is  found  that  even  here  it  is  impossible  to  remove  scale  which 
adheres  closely  or  which  is  very  thick.  I  conclude,  then,  that 
the  wire  brush  is  not  sufficient  and  that  its  use  should  be  pre- 
ceded by  scraping.  The  painter's  torch  is  sometimes  used  as 
an  accessory.  This  throws  a  jet  of  flame  on  the  surface  of  the 
metal,  and  as  the  rust  and  scale  become  much  more  heated  than 
the  metal  they  tend  to  crack  off  and  are  more  easily  removed, 
and  any  water  which  is  held  in  their  interstices  is  driven  off,  but 
of  course  the  hydrated  oxide  is  not  dehydrated  in  the  chemical 
•sense,  for  it  requires  a  much  higher  heat  to  do  this,  as  has  been 
already  explained.  Bridges  which  have  been  erected  can  usually 
be  cleaned  only  in  such  ways  as  have  been  just  described,  although 
on  some  railroads  bridges  in  place,  especially  old  ones,  are  cleaned, 
usually  in  part  only,  by  the  sand-blast.  Those  parts  of  the 


PROTECTION  OF  METALS  AGAINST   CORROSION.       197 

bridge  which  are  most  badly  rusted  are  cleaned  with  the  sand- 
blast, and  the  rest  of  the  bridge  with  scrapers  and  wire  brushes, 
on  the  theory  that  the  most  exposed  parts  need  the  most  care 
and  that  the  less  rusted  members  will  last  long  enough  with 
more  inexpensive  treatment,  which  is  doubtless  correct. 

Sand-blast. — The  most  thorough  and  perfect  manner  of 
cleaning  metal  in  any  mechanical  way  is  by  the  sand-blast,  which 
is  a  stream  of  particles  of  sand  thrown  with  great  velocity  against 
the  surface;  the  grains  of  sand  have  sharp  cutting  edges  and 
partly  by  cutting  and  partly  by  the  impact  or  hammering  of 
these  little  pieces  of  quartz  the  scale  and  rust  are  cut  and  broken 
up  and  removed.  It  has  been  proposed  to  throw  the  sand  with 
levers,  as  from  a  catapult,  or  by  centrifugal  force,  but  the  only 
practical  way  is  to  mix  it  with  an  escaping  current  of  compressed 
air,  which  carries  it  along  with  great  velocity,  hence  the  name. 
This  method  of  applying  power  for  cutting  and  abrasion  was 
invented  by  Gen.  Benj.  G.  Tilghman,  of  Philadelphia,  and 
was  patented  by  him  Oct.  18,  1870,  the  patent  being  numbered 
108,408. 

Among  the  most  important  claims  granted  by  that  patent 
were  the  following: 

1.  The  cutting,  boring,  dressing,  engraving,  and  pulverizing 
of    stone,  metal,  glass,  pottery,  wood,  and  other  hard  or  solid 
substances  by  sand  used  as  a  projectile,  when  the  requisite  veloc- 
ity has  been  imparted  to  it  by  any  suitable  means. 

2.  The  artificial  combination  of  a  jet  or  current  of  steam, 
air,  water,  or  other  suitable  gaseous  or  liquid  medium,  with  a 
stream  of  sand,  as  a  means  of  giving  velocity  to  the  sand  when 
the  same  is  used  as  a  projectile  as  a  means  of  cutting,  boring, 
dressing,  etc.,  etc. 

7.  When  a  jet  or  current  of  steam,  air,  water,  or  any  other 
suitable  gaseous  or  liquid  medium  is  employed  to  give  velocity 
to  sand  used  as  a  projectile,  as  a  means  of  cutting,  boring,  dress- 
ing, etc.,  the  use  of  the  following  devices  for  introducing  the  sand 
into  the  jet  of  steam,  air,  water,  etc.  First,  the  suction  produced 
by  the  jet  of  steam,  air,  water,  etc.  Second,  a  strong,  close  vessel, 


198 


TECHNOLOGY   OF  PAINT  AND    VARNISH. 


or  sand-box,  into  which  the  pressure  of  the  steam,  air,  water, 
etc.,  is  introduced  and  through  which,  when  desired,  a  current 
of  it  may  be  made  to  pass. 

It  is  obvious  from  the  foregoing  that  there  is  no  existing 
patent  on  the  process,  and  while  there  is  some  patented  apparatus 
which  is  preferred  by  some  of  the  people  who  use  the  process, 
this  is  equally  true  of  a  very  large  proportion  of  all  machinery 
in  use. 

The  Tilghman  apparatus  as  improved  and  patented  by 
Mathewson  is  shown  in  section  in  the  following  illustration, 

MATHEWSON'S  SAND-BLAST. 

(TRADE  NAME,  TILQHMAN.) 


Hose  with 
Special  End 


In  this  apparatus  a  slotted  slide,  operated  by  a  lever,  regulates 


PROTECTION  OF  METALS  AGAINST  CORROSION.       199 

the  quantity  of  sand  introduced  into  the  current  of  air.    This 
machine  was  patented  Dec.  25,  1894;  No.  531,379. 

In  the  Paxson- Warren  machine,  shown  in  the  next  figure,  the 


Pipefrom         WARREN'S  SAND-BLAST. 

Air  Receiver        (TRADE  NAME,  PAXSON-W.ARREN4 


Straight  Hose 


feed  of  the  sand  is  regulated  by  a  revolving  piece,  or  valve,  which 
covers  the  opening  in  the  bottom  of  the  hopper  to  the  extent 
desired  to  let  the  proper  quantity  of  sand  fall  through  it  and  into 
the  air-pipe. 

In  the  machine  patented  by  J.  M.  Newhouse  of  Columbus,  Ohio, 
shown  in  the  illustration  on  the  next  page,  the  sand  passes  from 
the  hopper  at  the  bottom  through  an  annular  opening  around  the 
end  of  a  nozzle-shaped  steel  piece,  which  decreases  in  its  outer  cir- 


200 


TECHNOLOGY  OF  PAINT  AND   VARNISH. 


cumference  toward  the  end  and,  by  raising  or  lowering  it,  this 
annular  opening  may  be  increased  or  diminished  in  size.  The 
distinguishing  feature  of  this  appliance  is  the  use  of  this  nozzle  as 
a  siphon  with  its  perforation  as  shown.  The  small  holes  permit 
part  of  the  air  which  flows  through  the  small  pipe  and  the  siphon 


THE  NEWHOUSE  SAND-BLAST. 

to  escape  outwardly  through  the  surrounding  sand,  thus  stirring 
it  up  and  preventing  it  from  clogging  the  opening.  A  similar 
siphon,  without  the  perforations,  is  placed  in  the  air-pipe. 

The  process  of  cleaning  with  the  sand-blast  is  essentially 
as  follows:  Air  at  a  pressure  of  20  to  25  Ibs.  per  sq.  in.  is  fur- 
nished by  any  suitable  air-compressor.  If  we  assume  that  we 


PROTECTION  OF  METALS  AGAINST  CORROSION.       2OI 

will  use  a  discharging-nozzle  T9g-  in.  internal  diameter,  when 
new,  each  such  nozzle  will  require  120  cu.  ft.  of  air  per  minute, 
measured  at  atmospheric  pressure  compressed  to  show  a  pres- 
sure of  15  Ibs.  per  sq.  in.  at  the  nozzle.  This  is,  however,  to 
be  regarded  as  a  minimum,  for  it  is  advisable  to  use  a  somewhat 
higher  pressure,  say  20  Ibs.,  and  the  nozzle  rapidly  wears  away 
until  it  reaches  a  diameter  of  f  in.,  at  which  it  will  discharge 
nearly  twice  as  much  as  when  new,  so  that  in  practice  it  is  well 
to  provide  an  air-compressor  handling  240  cu.  ft.  of  air  per  minute 
and  compressing  the  same  to  20  Ibs.  per  sq.  in.  Recent  work 
has  shown  that  a  pressure  as  high  as  35  Ibs.  per  sq.  in.  is  desira- 
ble and  economical  for  removing  heavy  scale,  which  a  blast  at  a 
lower  pressure  will  not  remove. 

Into  this  current  of  air  dry  sand  is  introduced  at  the  rate  of 
about  10  cu.  ft.  of  sand  per  hour  for  each  such  nozzle,  or  i  cu.  ft. 
of  sand  to  1000  cu.  ft.  of  air.     The  sand  must  be  artificially 
dried;     some    operators    use    coarsely   powdered    quartz.     This, 
latter  can  be  used  five  times  in  succession;    and  in  general  the 
sand  may  be  used  until  it  is  broken  up  into  a  powder  too  fine 
for  use.     In  the  plants  which  the  writer  has  inspected  the  sand 
and  air  are  carried  to  the  nozzle  through  a  heavy  rubber  hose 
about  2\  in.  diameter.      This  is  not  worn  away  by  the  current 
as  a  metal  pipe  would  be,  but  it  is  necessary  that  the  air  should 
not  be  hot,  as  this  would  rapidly  injure  the  hose.     The  nozzles 
are  short  pieces  of  extra-heavy  iron  pipe  and  have  to  be  renewed  at 
frequent  intervals.     From  data   furnished  me  by  Naval   Con- 
structor Bowles  I  find  that  the  cost  of  cleaning  the  bottom  of  a 
ship  in  dry  dock  amounted  to  about  4  cents  per  square  foot,  but  this 
was  done  with  an  experimental  plant,  and  the  method  of  drying- 
the  sand,  which  was  used  only  once,  was  costly,  and  the  cost 
would  certainly  have  been  reduced  to  3  cents  per  square  foot  if  a 
permanent  plant  had  been  in  use.     Since  the  installation  of  a 
permanent  plant  no  work  has  been  done  of  sufficient  magni- 
tude to   give   figures.     This   was   an  exceedingly  rusty  surface, 
but  with  this  same  experimental  plant  the  mill-scale  was  removed 
from  3,155  sq.  ft.  of  surface  of  steel  plates  at  a  cost  of  $17.60, 


202  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

or  about  i  cent  per  square  foot  anci  at  the  rate  of  4!  sq.  ft.  per 
minute  per  nozzle. 

It  may  be  well  to  add  that  in  all  the  work  referred  to,  which 
was  practically  field  work,  being  carried  on  out  of  doors  and 
with  a  somewhat  portable  plant,  the  labor  amounted  to  one  man 
to  hold  each  nozzle,  one  man  to  attend  to  each  two  sand-boxes, 
and  one  man  to  clean  up  and  carry  sand  for  each  four  nozzles. 
The  supply  of  compressed  air  is  an  expense  of  a  different  sort,  as 
is  also  in  field  work  the  matter  of  staging,  etc.,  but  all  are  included 
in  the  prices  given.  It  seems  reasonable  to  suppose  that  where 
many  pieces  of  metal  of  the  same  general  character  are  to  be 
treated  in  a  shop  fitted  up  for  the  purpose,  contrivances  may  be 
introduced  which  will  do  away  with  a  considerable  part  of  the 
labor. 

4  Pickling. — Iron  and  steel  may  also  be  cleaned  by  pickling  in 
acid  and  the  subsequent  removal  of  the  latter.  This  may  be  done 
in  the  following  manner:  The  pieces  of  metal  which  have  been 
made  ready  for  assembling  are  immersed  in  hot  dilute  sulphuric 
acid  having  a  strength  of  25  to  28  per  cent.  Some  use  acid  of  20 
per  cent.  It  is  kept  in  this  until  the  whole  surface  is  free  from 
rust  and  scale.  This  will  take  from  six  to  twelve  minutes.  If  the 
pieces  of  metal  are  somewhat  rusty,  so  that  rust  has  started 
underneath  the  scale,  the  shorter  time  will  be  found  sufficient, 
but  if  it  consists  of  plates  covered  with  closely  adherent  blue  or 
iridescent  rolled  scale,  the  longer  time  will  be  necessary,  since 
this  scale  is  itself  insoluble  in  acid  and  is  removed  by  the  latter 
penetrating  the  innumerable  minute  cracks  in  the  scale  and 
attacking  the  iron  underneath,  thus  mechanically  throwing  off 
the  scale.  If,  on  the  other  hand,  the  iron  is  uniformly  rusty,  this 
coating  of  hydrated  oxide  readily  dissolves  in  acid,  and  in  fact 
a  weaker  acid  of  10  to  12  per  cent,  might  be  used,  although 
the  stronger  acid  is  quite  safe  but  will  require  a  shorter  time.  It 
has  been  suggested  that  it  is  desirable  to  previously  clean  the 
metal  with  caustic  alkali  from  all  grease,  etc.,  but  if  acid  of  the 
above  strength  is  used  and  kept  as  hot  as  possible  this  will  not  be 
necessary.  As  soon  as  the  acid  has  reached  the  iron  in  all  parts 


PROTECTION  OF  METALS  AGAINST  CORROSION.       203 

of  the  surface,  the  metal  is  taken  out  and  washed  by  jets  of  water 
discharged  against  it  under  high  pressure,  not  less  than  100  Ibs. 
per  square  inch  and  much  better  if  double  that.  In  this  way  the 
acid  may  be  thoroughly  removed. 

In  Germany  it  is  said  to  be  customary  to  use  acid  of  9  or  10 
per  cent,  cold,  and  the  metal  is  left  in  it  five  hours.  This  makes 
a  much  larger  plant  necessary  and  has  no  advantages. 

If  it  is  attempted  to  remove  the  acid  by  soaking  the  metal 
in  still  water,  the  following  difficulty  is  encountered:  the  iron 
becomes  immediately  coated  with  a  gummy  or  colloidal  substance, 
very  difficult  to  remove.  What  this  is,  is  not  known  to  the  writer, 
but  is  it  well  known  that  there  are  a  number  of  insoluble  or  diffi- 
cultly soluble  compounds  of  iron  with  sulphuric  acid,  and  it  is 
probable  that  some  of  these  are  precipitated  on  the  surface  of  the 
iron  when  water  removes  the  excess  of  acid,  but  if  a  jet  of  water 
is  used  the  mechanical  effect  is  to  remove  trie  adherent  ferrous 
sulphate  at  the  same  instant,  leaving  a  clean  metallic  surface. 
It  is  also  possible  that  if  the  acid  contains  arsenic,  as  is  the  case 
with  much  of  the  acid  made  from  pyrites,  this  may  also  be  pre- 
cipitated on  the  surface.  In  fact,  it  is  sure  to  be,  and  acid  free 
from  arsenic  should  always  be  used  for  this  purpose,  and  as  a 
matter  of  practice  it  is  insisted  on  by  many. 

It  is  often  difficult,  and  sometimes  impracticable,  to  pickle  steel 
high  in  carbon  and  cast  iron  containing  graphitic  carbon,  on  account 
of  the  deposit  of  a  film  of  carbon  like  stove-blacking  on  the  surface. 
Muriatic  (chlorhydric)  acid  has  been  used  instead  of  sulphuric, 
but  it  is  not  well  suited  for  the  purpose,  being  much  more  expen- 
sive and  difficult  to  remove.  It  also  forms  a  gummy  coating  on 
the  iron,  worse  than  that  with  sulphuric,  and  in  the  subsequent 
alkaline  treatment  it  must  be  removed  by  caustic  soda  instead 
of  lime,  or  sometimes  by  a  solution  of  sulphate  of  zinc. 

After  the  iron  has  been  freed  from  sulphuric  acid  in  the  man- 
ner just  described,  it  is  put  in  a  bath  of  lime-water  or  milk  of 
lime,  boiling  hot  (it  is  very  important  that  it  should  be  hot),  and 
left  there  long  enough  to  reach  the  temperature  of  the  liquid. 
It  is  then  removed  to  an  oven  and  dried,  after  which  the  lime  is 


204  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

brushed  off.  If  desired,  the  lime  may  be  removed  by  washing  before 
putting  in  the  oven.  In  this  case  it  will  be  found  that  the  surface, 
which  is  perfectly  clean  and  bright,  rusts  very  easily  and  quickly, 
whereas  if  the  lime  is  removed  by  drying  and  brushing,  the  sur- 
face is  much  less  likely  to  rust,  although  even  then  it  rusts  easily 
and  should  be  painted  immediately. 

For  most  of  the  foregoing  information  relating  to  pickling  I 
am  indebted  to  Mr.  E.  G.  Spilsbury,  who  has  had  extensive 
experience  in  this  work  -both  in  Europe  and  the  United  States, 
and  has  applied  the  process  to  structural  steel  (bridge)  work,  as 
well  as  to  wire  and  wire  rods. 

Some  of  the  largest  work  recently  done  has  been  treated  as 
follows :  The  steel  as  it  came  from  the  mill  was  put  in  hot  10  per 
cent,  caustic  soda  solution  until  all  the  grease  and  oil  came  off; 
with  this  came  all  the  dirt,  with  which  the  shop  grease  had  become 
mixed,  and  an  appreciable  amount  of  scale,  making  altogether 
a  bulky  sludge.  Next  the  steel  was  washed  with  boiling  water; 
then  it  was  put  in  hot  10  per  cent,  sulphuric  acid  until  the  metal 
surface  was  everywhere  exposed;  after  which  it  was  dipped  in 
boiling  water,  then  in  hot  10  per  cent,  solution  of  carbonate  of 
soda,  then  well  washed  in  hot  water,  and  finally  dried  in  an  oven. 
The  results  were  all  that  could  be  desired. 

Much  detailed  information  concerning  the  use  of  the  sand 
blast  in  cleaning  structural  steel  may  be  found  in  the  paper  on 
the  subject  by  Mr.  George  W.  Lilly,  in  the  Transactions  of  the 
American  Society  of  Civil  Engineers  in  1903  and  in  the  ensuing 
discussion. 

Treatment  at  the  Mill. — Many  engineers  believe  that  the 
time  to  begin  the  protection  of  steel  is  at  the  rolling-mill,  before 
the  metal  is  cold.  It  is  said  that  careful  methods  of  rolling  will 
prevent  the  formation  of  thick  scale  and  that  most  of  the  scale  may 
be  removed  as  the  metal  comes  from  the  rolls,  immediately  after 
which  the  hot  surface  (at  a  black  heat)  is  to  be  sprayed  with  oil 
or  varnish  or  paint  and  the  heat  remaining  in  the  metal  will  be 
enough  to  bake  this  before  the  metal  becomes  entirely  cold,  thus 
producing  a  coated  and  protected  surface,  which  insures  freedom 


PROTECTION   OF  METALS  AGAINST  CORROSION.        205 

from  rust  for  a  period  of  at  least  some  weeks,  during  which  the 
metal  may  be  built  up  into  riveted  members  and  made  ready  for 
painting.  The  details  of  this  plan  have  not  at  present  been  worked 
out  in  practice,  but  there  is  no  doubt  in  my  mind  that  it  is  a  very 
desirable  thing  and  I  believe  it  to  be  practicable.  Putting  bars  of 
various  sections  through  straightening  rolls  has  been  proposed 
as  a  means  of  removing  the  scale.  It  will  remove  thick  scale  and 
will  loosen  all  but  the  most  closely  adherent  thin  scale.  This  may 
be  seen  where  sheets  of  steel  are  rolled  in  a  boiler-shop  or  in  mak- 
ing large  pipe.  Coatings  have  been  very  successfully  applied  to 
such  surfaces. 

Shop-painting. — In  bridge  work  and  the  like,  if  it  is  decided 
to  clean  by  pickling  or  sand-blasting,  it  is  a  question  as  to  when 
this  should  be  done.  If  it  is  done  when  the  metal  comes  from 
the  mill  (supposing  that  it  has  not  been  coated  hot  in  the  way 
just  mentioned)  it  will  be  necessary  to  do  something  to  it  at  once 
to  prevent  its  rusting;  for  pickled  or  sand-blasted  iron  will  begin  to 
rust  almost  immediately  and  the  iron  has  to  be  at  least  a  week 
in  the  shop  before  it  can  be  painted  after  assembling.  What 
can  be  done  to  it  ?  Probably  a  coat  of  linseed-oil  will  be  applied. 
Paint  will  be  objected  to  by  the  shopmen  and  the  inspectors  will 
demand  a  transparent  coating.  Boiled  oil  is  commonly  used  for 
any  such  purpose  because  it  dries  rapidly,  but  it  is  less  durable 
than  raw  oil,  and  it  is  the  common  opinion  of  the  manufac- 
turers of  mixed  paints,  whose  opinions  in  this  matter  are  en- 
titled to  great  weight,  that  boiled  oil  is  less  durable  than  raw 
oil  to  which  enough  drier  has  been  added  to  make  its  drying 
qualities  equal  to  boiled  oil.  The  drier  should  probably  be  one 
made  at  low  temperatures.  The  cleaned  surface  may  then 
receive  a  coat  of  such  oil  and  allowed  a  day  or  two  to  dry.  But 
it  must  be  observed  that  oil  does  not  dry  to  a  hard  film,  but  is 
soft  and  rather  sticky,  and  probably  a  very  elastic  varnish  would 
be  better  because  cleaner;  less  likely  to  be  contaminated  with 
dirt  and  machine-oil  in  the  shop.  Probably  the  increased  cost 
will  be  a  barrier  to  its  use.  It  might,  and  I  think  should,  be  very 
thin,  as  it  would  then  be  harder,  and  it  is  not  depended  on  for 


206  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

permanent  protection,  but  it  should  be  of  good  quality  as  the 
foundation  for  all  subsequent  painting. 

A  much  better  plan  is  to  defer  the  pickling  or  sand-blasting 
until  the  structural  steel  has  been  long  enough  in  the  shop  to 
have  been  cut  to  required  dimensions  and  all  the  holes  punched 
or  bored  and  otherwise  made  ready  for  assembling.  Then 
let  it  be  removed  from  the  shop  to  the  building  where  the  sand- 
blasting is  done  (for  it  should  be  under  shelter),  cleaned,  and 
painted.  It  is  practicable  to  have  it  painted  at  this  stage  unless, 
for  purpose  of  inspection,  it  is  thought  better  to  have  it  oiled, 
or,  better,  varnished.  When  the  painting  or  varnishing  has  been 
done  and  two  or  three  days  for  the  coating  to  begin  to  dry  have 
elapsed,  it  may  be  carried  back  to  the  shops  and  riveted  up  into 
members,  care  being  taken  to  again  paint,  and  thoroughly,  all 
surfaces  which  will  hereafter  be  inaccessible,  for  rusting  in  riveted 
joints  not  only  weakens  but  impairs  the  rigidity  of  the  structure. 
It  is  only  fair  to  say  that  I  have  been  told  by  engineers  of  bridges 
who  have  had  much  experience  in  taking  down  riveted  work 
that  it  is  uncommon  for  riveted  joints  to  be  dangerously  rusted 
and  that  the  webs,  rods,  and  other  extended  parts  rust  off  before 
the  joints  give  way.  This  is  partly  because  there  is  more  metal 
at  the  joints  than  elsewhere  and  probably  partly  because  care  is 
usually  taken  to  paint  these  surfaces  heavily,  and  the  paint  is 
mechanically  protected  by  the  location  from  external  injury. 

Shop-marks. — Where  it  is  undesirable  to  paint  portions  of 
the  surface  on  account  of  shop-marks,  care  should  be  taken  that 
these  marks  are  as  compact  and  small  as  is  reasonable  and  to  see 
that  they  receive  an  extra  coat  in  the  final  painting.  Planed 
and  turned  surfaces  are  at  this  time  coated  with  a  non-drying 
grease,  commonly  a  mixture  of  white  lead  and  tallow,  or  a  min- 
eral grease  similar  to  vaseline,  which  many'  prefer. 

Crevices. — There  are  also  found  many  crevices  which  will 
be  inaccessible  after  erection,  and  it  is  customary  to  fill  these 
with  a  fresh  mixture  of  neat  Portland  cement  and  water.  It  is 
possible  to  use  other  cementing  substances,  but  nothing  is  so  easily 
used  as  the  above,  and  it  is  good  enough. 


PROTECTION   OF  METALS  AGAINST  CORROSION.       207 

Shipping. — The  work  is  now  ready  for  shipment.  In  ship- 
ping, care  should  be  taken  to  avoid  scraping  off  the  paint  and  to 
avoid  nesting  the  pieces  except  with  packing  material  between 
them;  and,  as  has  been  already  said,  the  pieces  should  not  be 
laid  on  the  ground,  but  on  skids  or  trestles.  The  paint  should 
be  reasonably  dry  before  the  shipment  is  begun,  not  thoroughly 
dry,  but  it  should  have  its  initial  set  and  dry  enough  to  be  safely 
handled,  usually  in  two  or  three  days  after  the  paint  has  been 
applied,  sometimes  one  day  in  hot  weather. 

Striping  Coat. — The  materials  may  now  be  supposed  ready 
for  erection,  after  which  the  work  should  be  carefully  inspected, 
and  if  there  are  any  rusty  spots  these  should  be  thoroughly  cleaned 
and  painted,  and  any  places  where  the  paint  has  been  rubbed 
off  should  be  repainted,  and  at  this  time  all  exposed  edges  and 
angles  should  receive  an  extra  striping  coat  of  the  protective 
coating,  covering  the  edge  and  the  adjacent  surface  one  or  two 
inches  from  the  edge  on  each  side,  and  all  nuts,  bolt-heads, 
and  rivet -heads  should  receive  an  extra  coat.  This  may  be 
called  the  striping  coat  and  is  necessary  for  the  following 
reasons : 

When  paint  begins  to  dry  there  is  at  first  a  sort  of  skin  formed 
on  the  surface,  which  contracts,  and  on  rounded  surfaces  like 
rivet- heads  and  on  angles  and  edges  seems  to  press  away  the 
liquid  paint  beneath,  so  that  on  such  surfaces  there  is  less  than 
the  normal  amount.  The  same  tendency  to  contract  also  exists 
on  flat  surfaces,  but  in  this  case  it  is  a  balanced  tension  and  pro- 
duces no  effect.  There  is  besides  the  action  of  the  painter's 
brush,  which  presses  harder  on  such  places  and  draws  off  the 
paint;  but  that  this  is  not  the  main  cause  is  shown  by  the  fact 
that  pipe  sections  and  other  things  which  have  been  coated  by 
dipping  exhibit  the  same  appearance.  In  making  paint  tests, 
it  is  necessary  to  leave  out  of  account  a  strip  about  an  inch  wide 
along  the  edges  of  the  plate  unless  that  portion  has  received 
an  extra  coat,  and  the  fact  is  well  known  to  inspectors  that  such 
surfaces  are  always  thinly  coated.  The  extra  striping  coat  is 
therefore  necessary  if  we  are  to  have  two  full  coats  or  their 


208  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

equivalent  over  the  whole  surface,  and  it  is  the  more  impor- 
tant because  these  portions  are  more  exposed  than  the  flat  sur- 
faces. 

When  this  striping  coat  has  become  dry  (two  weeks  or  longer  if 
possible  after  its  application),  another  full  coat  of  the  protective 
coating  should  be  applied  to  the  whole  surface.  Of  course,  if  a 
coat  of  oil  or  thin  varnish  has  been  applied  in  the  shop  instead  of 
the  regular  protective  coating,  another  full  coat  of  the  latter  will 
be  necessary  after  erection,  and  the  striping  coat  may  intervene 
between  these  two  full  coats.  If,  during  erection,  any  small 
cavities  are  produced  they  should  be  filled  as  already  described, 
and  any  large  ones  should  be  drained  by  making  suitable  open- 
ings. Care  should  be  taken  that  no  undrained  places  are  left 
which  may  fill  with  rain  or  ice ;  the  latter  by  its  mechanical  action 
is  likely  to  tear  off  the  best  paint. 

If  the  preceding  directions  have  been  followed,  the  structure 
has  two  full  coats  of  a  protective  coating  and  is  ready  for  decora- 
tive painting,  if  any  is  desired.  If  not,  it  should  have  a  third 
coat  of  the  protective  coating.  Two  or  three  or  even  six  months 
may,  however,  be  allowed  to  elapse  before  this  final  painting  is 
done.  The  structure  may  now  be  regarded  as  finished  and  turned 
over  to  the  maintenance  department,  who  should  watch  it  care- 
fully and  repaint  it  before  it  begins  to  rust,  or,  at  least  (perhaps 
better),  touch  up  any  doubtful  places  and  so  avoid  any  general 
repainting.  I  believe  that  a  structure  treated  in  this  way  would 
be  easily  maintained  in  practically  perfect  condition  at  a  cost  so 
low  as  to  be  unimportant.  It  should  not  be  forgotten  in  con- 
nection with  this  whole  subject  that  paint  should  not  be  applied 
in  freezing,  rainy,  or  misty  weather,  or  to  surfaces  which  are  not 
dry  and  clean,  but  this  is  true  of  all  painting.  It  is  sometimes 
necessary  to  apply  paint  in  cool  weather.  It  is  then  allowable 
to  heat  the  paint  to  a  temperature  of  150°  F.,  which  will  be 
found  much  better  than  thinning  it. 

It  is  folly  to  expect  any  general  agreement  as  to  what  is 
the  composition  of  the  best  coating  for  structural  metal.  Those 
which  are  practically  in  use  are: 


PROTECTION   OF  METALS  AGAINST  CORROSION.       209 

1.  A  variety  of  mixtures,  of  which  coal-tar  dissolved  in  ben- 
zole or  dead-oil  may  be  taken  as  the  type. 

2.  Paints    made   with   linseed-oil   or   an   alleged   substitute, 
and  pigment ;  containing  some  drier  and  usually  some  varnish. 

3.  Varnishes. 

4.  Varnish  and  pigment  paints  (the  so-called  varnish  enamels). 
Other  materials  are  used  on  water-pipes,  but  these  will  receive 
separate  discussion. 

Coatings  of  the  first  class  need  very  little  discussion.  They 
are  used  because  they  are  cheap.  I  have  heard  of  a  mixture 
of  asphalt  and  mineral  oil  which  cost,  exclusive  of  packages,  only 
seven  cents  per  gallon,  which  was  used  on  some  railway  bridges; 
the  labor  of  applying  it,  and  the  constant  repainting  which  was 
required,  made  the  final  cost  of  maintenance  so  great  that  the 
authorities  changed  to  the  use  of  a  paint  costing  a  dollar  and 
a  half  a  gallon.  Most  of  the  so-called  asphaltum  varnishes 
used  on  metal-work  come  under  this  heading.  They  contain 
frequently  nothing  more  expensive  than  coal-tar  or  petroleum 
residues,  and  are  thinned  frequently  with  kerosene.  Rarely 
these  mixtures  are  made  with  asphaltum  and  softened  with  palm- 
oil  stearine,  or  something  of  that  sort,  and  thinned  with  benzine; 
such  a  mixture  may  be  very  good  for  temporary  use,  being 
impervious  as  long  as  its  elasticity  remains,  and,  unlike  much  coal- 
tar,  being  free  from  acid  which  will  attack  the  iron.  Some  of 
the  cheap  coal-tar  mixtures  are  actively  corrosive;  some  are 
mixed  with  pulverized  lime  to  remove  the  acidity.  It  is  by  no 
means  unusual  for  a  contractor,  especially  on  public  work  or 
on  work  where  the  inspection  is  not  good,  to  contract  for  the  use 
of  a  good  paint,  and  use  instead  some  of  these  excessively  cheap 
and  worthless  mixtures.  I  would  not  include  adulterated  paints 
under  this  heading,  but  among  those  paints  which  they  imitate; 
and  I  do  not  say  that  some  of  these  mixtures  or  compounds  are 
not  good  enough  for  temporary  use;  and  not  a  little  steel  is 
v.sed  in  this  way.  But  in  general,  it  may  be  fairly  said  that  these 
mixtures  are  not  as  economical  as  better  paints,  and  hence  are 
not  suited  for  general  use. 


210  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

Oil  Paints. — In  the  second  class,  that  of  oil  paints,  among 
which,  as  a  matter  of  convenience,  I  will  include  red  lead  and 
oil  although  this  is  considerably  different  from  ordinary  paints, 
are  found  the  most  commercially  important  of  the  preservative 
coatings.  It  will  appear  before  this  essay  is  finished  that  the 
author  believes  in  the  use  of  varnish  paints  as  the  best,  but  it 
must  be  observed  that  linseed-oil  is  the  elastic  base  of  varnish, 
and  as  the  varnish-resins  are  more  costly  than  oil,  and  as 
any  labor  expended  in  making  varnish  increases  the  cost  of  the 
materials  contained  in  it,  so  it  is  that  a  straight  linseed-oil  paint 
may  be  made  at  a  lower  price  than  a  varnish  paint  and  is  the  best 
paint  that  can  be  hard  at  the  price.  When  we  are  able  to  say  that 
such  a  paint  is  really  a  good  paint  and  that  it  is  the  best  to  be 
had  at  the  price,  we  have  given  reasons  for  its  use  which  no 
possible  arguments  can  overthrow,  though  they  may  modify  their 
application. 

An  oil  paint  is  composed  of  a  pigment  mixed  with  a  liquid  or 
vehicle,  which  consists  usually  of  raw  linseed-oil  to  which  has  been 
added  5  to  10  per  cent,  by  volume  of  liquid  drier,  this  latter  con- 
taining usually  both  lead  and  manganese,  and  either  turpentine  or 
benzine  as  the  volatile  part.    This  mixture  of  oil  and  drier  is  not 
very  likely  to  change  if  kept  from  the  air  and  is  chemically  unaf- 
fected by  most  pigments;  hence  an  oil  paint  has  excellent  keeping 
qualities.     Of  course  the  pigment  will  in  time  settle  to  the  bottom, 
but  commonly  it  can  be  stirred  up  again;  however,  a  paint  should 
always  be  used  up  before  it  is  injured  in  this  way.    Containing 
little  volatile  matter  it  does  not  evaporate,  and  the  oil  works 
freely  under  the  brush,  more  so  than  the  best  varnish,  so  that 
an  oil  paint  is  the  easiest  to  apply  of  all  paints.    This  in  itself  is  a 
great  advantage,  for  it  is  easier  both  physically  and  mentally  to 
put  on  a  good-looking  coat  of  oil  paint  than  of  any  other.    This 
quality  of  working  freely  and  sweetly  under  the  brush  is  the  best, 
thing  about  an  oil  paint,  and  this  alone  is  the  reason  why  these 
have  displaced  the  varnish  paints  in  the  work  of  modern  artists, 
while  probably  all  the  so-called  oil  paintings  of  the  great  painters 
of  the  middle  ages  were  done  in  pleo-resinous  varnish.     Oil  is, 


PROTECTION   OF  METALS  AGAINST  CORROSION.       211 

when  spread  in  a  thin  film,  very  slow  to  set,  and  when  it  finally 
begins  to  set  it  goes  on  rapidly  until  the  paint  is  hard  enough  to 
handle;  the  thorough  hardening  takes  a  long  time,  perhaps  a 
year.  This  slowness  of  setting  facilitates  working  with  a  brush, 
and,  especially  on  wood,  gives  it  time  to  penetrate  the  pores  of 
the  surface  to  which  it  is  applied.  A  coat  of  oil  is,  therefore,, 
often  used  on  wood  as  a  priming  coat  even  where  varnish  is  sub- 
sequently to  be  used.  On  account  of  its  remarkable  fluidity 
linseed-oil  may  be  mixed  with  a  large  proportion  of  pigment,  and 
if  this  pigment  is  very  cheap  it  may  actually  reduce  the  cost,  and 
if  it  is  dear  the  oil-paint  still  usually  has  advantages  in  price 
because  of  the  lower  price  of  oil  than  of  varnish^  and,  as  it  carries 
more  pigment,  its  covering  power,  or  opacity,  is  greater.  Any- 
thing which  enables  two  coats  to  take  the  place  of  three  is  a  great 
advantage,  for  the  cost  of  labor  is  an  important  item,  sometimes 
being  much  more  than  that  of  the  paint.  Oil  is  usually,  when 
fresh,  more  nearly  colorless  than  varnish,  and  on  that  account 
displays  well  the  color  of  the  pigment.  This  advantage,  however,, 
disappears  very  shortly,  for  oil  paints  quickly  become  dull  and 
show  the  effect  of  the  weather  more  than  varnish  paints. 

The  possible  supply  of  linseed-oil  is  unlimited.  Flax  will  grow 
anywhere  that  any  cereals  will,  and  when  the  seed  is  high  in  value 
the  acreage  quickly  increases,  so  the  oil  is  subject  to  large  and 
rapid  fluctuations  in  price.  When  it  is  high,  there  is  a  strong 
temptation  to  adulterate  it  or  to  substitute  something  for  it. 

Oil  Substitutes  and  Adulterants. — The  most  common  adul- 
teration is  with  mineral  oil,  but  substitutes  are  from  time  to  time 
proposed,  the  most  important  probably  being  fish-oil.  This  is. 
normally  a  non-drying  oil,  but  it  may  be  cooked  with^lead  and 
manganese  and  made  into  a  slowly  drying  oil.  It  has,  partly  by 
blowing  air  through  it  and  partly  by  treating  it  with  sulphur  at 
a  moderately  high  temperature  (vulcanizing) ,  been  converted  into 
an  elastic  solid  substance  which  is  soluble  in  kerosene  of  low 
boiling-point  and  thus  has  been  made  an  oil  which  dries,  like  a 
spirit  varnish,  by  evaporation  of  the  solvent.  The  first  of  these 
oils,  the  fish-oil  " boiled"  with  driers,  is  said  by  some  very  good. 


212  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

authorities  to  be  a  good  addition  to  the  extent  at  least  of  20 
per  cent,  to  linseed-oil  for  making  roof  paints,  its  slower  drying 
not  being  noticeable  in  this  case,  and  an  advantage  of  greater 
elasticity  is  claimed.  This  may  be  so.  I  have  no  experience  in  the 
matter,  but  I  think  this  is  believed  by  some  very  honest  and  very 
well-informed  makers.  As  to  the  other  preparation,  it  is  well 
thought  of  by  some  users,  but  in  the  cases  which  I  have  had 
opportunity  to  examine  it  has  not  been  equal  to  linseed-oil. 
Most  of  the  so-called  substitutes  are  various  mixtures  of  mineral 
oil,  fish-oil,  rosin,  rosin-oil,  and  rosin  varnish.  They  are  mainly 
sold  to  be  used  surreptitiously  as  adulterations  or  substitutes 
for  linseed-oil,  but  from  time  to  time  are  put  out  boldly  with  a 
flourish  of  trumpets  as  a  new  and  improved  variety  of  paint  oil, 
are  sold  for  a  time  to  the  unwary,  and  then  are  forgotten.  There 
is  no  oil  worthy  to  be  compared  with  linseed-oil  for  paint. 

As  has  been  stated  in  the  chapter  on  driers,  the  objection  to 
these  preparations  is  the  danger  that  they  may  continue  to  act 
after  the  film  has  become  properly  oxidized.  But  a  paint  which 
dries  slowly  makes  a  rather  soft  film  and  is  without  lustre,  so  it 
is  common  to  add  to  it  a  quantity  of  varnish,  which  hardens  the 
film  and  makes  it  smooth  and  shining.  If  this  varnish  is  made  of 
good  materials  it  improves  the  paint  in  every  way  except  working 
quality  and  covering  power  and,  in  the  amount  generally  used, 
does  not  sensibly  injure  it  in  these  respects.  Such  a  varnish 
ought  not,  however,  to  be  made  of  rosin,  but  of  some  of  the  true 
varnish-resins,  and  it  will,  in  the  nature  of  things,  add  to  the  cost 
of  the  paint.  A  cheap  rosin  varnish  is  often,  I  fear  I  might  say  com- 
monly, used  for  this  purpose,  and  is  bought  by  the  paint-maker 
at  less  than  the  price  of  oil,  sometimes  at  half  the  price  of  oil. 
The  worse  it  is  the  greater  is  the  temptation  to  use  it  to  excess; 
in  fact,  any  varnish  of  this  sort  is  an  excess. 

Lead  Paints. — As  a  rule  there  is  no  chemical  action  between 
oil  and  pigments,  but  to  this  there  are  exceptions.  Action  un- 
doubtedly occurs  between  oil  and  white  lead,  probably  between 
the  oil  and  the  lead  hydrate,  which  constitutes  at  least  a  quarter 
of  the  pigment.  This  takes  place  slowly,  and  painters  prefer 


PROTECTION   OF  METALS  AGAINST  CORROSION.       213 

white- lead  paint  which  has  been  ground  for  a  long  time  and  believe 
that  it  is  more  durable.  This  change  is  said  to  be  due  to  resini- 
fication  of  the  oil,  converting  it  into  a  sort  of  varnish;  chemically 
it  would  seem  that  it  should  be  a  saponification  resulting  in  a  lead 
soap,  which  would  dissolve  in  the  unchanged  oil.  I  am  not  aware 
that  any  careful  chemical  study  has  been  made  of  the  subject. 
Zinc  oxide  (white  zinc)  also  acts  on  oil,  but  in  a  much  less  degree, 
and  a  mixture  of  white  lead  and  white  zinc,  usually  in  the  propor- 
tion of  two  of  the  former  to  one  of  the  latter,  is  thought  to  be 
better  than  either  alone.  Zinc  works  more  freely  under  the 
brush,  but  its  covering  power  is  less. 

Red  Lead. — When  we  pass  on  to  red  lead,  which  is  an  oxide, 
we  find  that  the  pigment  and  the  oil  readily  unite;    in  red-lead 
paint  the  oxide  is  present  in  excess,  hence  all  the  oil  becomes 
combined.     If  red  lead  and  oil  are  mixed  and  sealed  up  in  an 
air-tight  can,  it  will  be  found  after  a  time  that  the  mixture  has 
solidified,  showing  that  the  oxygen  of  the  air,  which  is  the  har- 
dening agent  in  ordinary  paints,  is  not  necessary.     The  oil  is  not 
turned  to  linoxyn  but  is  completely  saponified  to  make  a  lead  soap, 
and  the  dry  paint  is  composed  of  unchanged  red  lead  cemented 
together  by  this  compound.     As  to  the  durability  of  the  latter, 
there  is  much  difference  of  opinion.     It  is  singular  that  every  one 
is  agreed  that  this  lead  soap,  or  linoleate  of  lead,  added  to  oil 
paint,  is  an  injury  to  it,  the  bad  results  increasing  with  the  amount, 
yet  it  cannot  be  denied  that  when  this  is  used  without  any  free  oil 
it  makes  a  cementing  material  or  binder  of  great  permanence,  less 
durable  perhaps  than  oil  alone,  but  worthy  to  be  compared  with 
it,  and  many  think  it  superior  to  oil.     It  is  natural  to  expect  it  to 
crumble  and  fall  off,  and  sometimes  it  does,  but  as  a  rule  it  does 
not,  but  adheres  to  the  iron  with  great  tenacity.     Not  much  is 
known  about  the  causes  which  promote  or  lessen  the  permanence 
of  red-lead  paint.     The  subject  needs  long  and  expensive  study. 
We  know  that  commercial  red  lead  is  of  variable  chemical  com- 
position, not  because  of  adulteration,  but  from  its  method  of 
manufacture.     It  is  a  mixture  of  the  peroxide  and  protoxide  of 
lead;  the  former  is  commonly  thought  to  be  the  most  important 


214  TECHNOLOGY   OF  PAINT  AND    VARNISH, 

and  characteristic  ingredient,  but  the  latter  is  present  to  an  extent 
which  varies  from  5  to  50  per  cent.  It  is  only  reasonable  to 
expect  different  results  from  different  mixtures  of  this  sort,  and 
no  one  seems  to  know  what  are  the  best  proportions.  It  is  said 
that  by  a  second  roasting  of  the  dry  red  lead  a  considerable  part 
of  the  litharge  in  it  may  be  changed  into  the  peroxide.  I  believe 
such  treatment  is  given  red  lead  for  making  storage  batteries- 
Such  red  lead  has  been  used  for  paint,  and  the  results  are  said 
to  be  encouraging.  It  has  long  been  known  that  the  protoxide 
(litharge)  and  glycerin  will  chemically  combine  when  mixed 
together  and  form  a  cement  of  great  value  used  for  cementing 
the  glass  plates  of  aquaria  and  the  like.  We  know  that  when  oil 
and  lead  oxide  combine  the  glycerin  of  the  oil  is  set  free.  This 
does  not  combine  with  the  peroxide,  but  in  the  presence  of  litharge 
it  probably  unites  with  it,  and  this  litharge- glycerin  cement  may 
play  an  important  part  in  the  action  of  the  lead  soap  with  which 
it  is  mixed.  Again,  it  may  be  that  the  oil  unites  with  the  litharge 
and  not  with  the  peroxide,  and  that  when  the  proportion  of  the 
former  is  low,  part  of  the  oil  dries  in  the  ordinary  way  by  air- 
oxidation.  There  is  nothing  against  this  supposition  in  the  be- 
havior of  the  paint.  And  yet  again  it  may  be  that  the  oil  com- 
bines with  the  litharge  and  that  a  large  proportion  of  the  latter  is 
necessary  to  get  the  best  results.  As  a  matter  of  fact,  we  know 
nothing  accurately  about  it.  I  have  been  told  by  a  manufac- 
turer of  red  lead  that  no  two  sorts  of  furnaces  will  give  the  same 
product,  and  that  different  men  will  get  different  products  from 
the  same  furnace  by  working  at  different  temperatures.  Enough 
has  been  said  to  explain  how  there  may  be  wide  differences  of 
opinion  in  regard  to  the  value  of  red  lead  as  a  paint  for  metal. 
On  one  point  there  is  a  substantial  agreement:  that  the  amount 
of  dry  red  lead  in  a  gallon  of  paint  should  be  as  large  as  practica- 
ble, from  18  to  30  Ibs.  to  a  gallon  of  finished  paint;  probably 
most  engineers  recommend  twenty-four  or  thereabouts.  On  an- 
other point  there  is  agreement  of  opinion — that  red  lead  is  the 
most  difficult  of  all  paints  to  apply,  and  this  again  may  be  an 
important  cause  of  failure.  The  working  qualities  of  the  paint 


PROTECTION   OF  METALS  AGAINST  CORROSION.       215 

are  improved  by  the  addition  of  lampblack,  which  probably  adds 
to  its  durability  also.  Because  this  paint  will  harden  in  closed 
packages  it  is  impracticable  to  prepare  it  in  advance  of  use;  it 
should  not  be  made  up  more  than  twenty-four  hours  ahead  of 
time,  and  it  is  better  if  mixed  on  the  spot  and  immediately  before 
using.  Various  methods  have  been  tried  to  avoid  this  difficulty; 
one  (patented)  mixture  contains  a  considerable  amount  of  glycerin 
instead  of  all  oil;  one  maker  mixed  two-thirds  red  lead  and  one- 
third  white  zinc:  this  will  keep  for  a  week  or  two;  others  add 
whiting  (carbonate  of  lime). 

Ready-mixed  Red  Lead. — Red  lead  is  also  mixed  with  oil  and 
allowed  to  stand  and  harden;  then  this  lead  and  oil  compound 
is  broken  up  and  reground  with  fresh  oil;  after  this  treatment  it 
sets  very  slowly  a  second  time.  This  is  analogous  to  breaking  up 
Portland  cement  after  it  has  begjn  to  set.  None  of  these  prepa- 
rations has  met  with  any  general  approval.  This  paint  is  often 
adulterated  with  oxide  of  iron,  which  is  much  cheaper.  Red-lead 
paint  adheres  well  to  iron  and  is  used  by  many  for  a  first  coat, 
having  some  good  paint  or  varnish  over  it  to  protect  it.  Being 
already  supersaturated  with  oxygen  it  is  not  attacked  by  that 
element;  it  would  seem  that  it  might  supply  oxygen  to  the  iron, 
thus  rusting  it,  but  it  does  not  do  so.  It  may  be  that  the  presence 
of  carbonic  acid  is  necessary,  and  this  is  kept  away  by  the  red 
lead,  which  itself  combines  with  it.  This  is,  in  fact,  a  common 
cause  of  the  whitening  of  red-lead  paint  exposed  to  the  weather, 
and  a  cause  of  its  destruction.  Red  lead  is  a  substance  which 
enters  with  great  energy  into  chemical  union  with  acids  of  almost 
all  kinds,  and  this  accounts  for  its  common  failure  when  used 
where  the  air  contains  them,  and  its  comparatively  excellent 
service  in  the  pure  air  of  the  country,  especially  away  from  the 
seaboard;  for,  as  nas  been  already  said,  the  air  near  the  sea 
contains  spray  of  sea-water  to  such  an  extent  that  the  natural 
fresh  waters  of  the  country  near  the  coast  contain  an  appreciable 
amount  of  common  salt,  the  proportion  of  which  decreases  as  the 
distance  from  the  sea  increases,  and  investigations  have  made  it 
possible  to  determine  and  draw  on  the  map  lines  of  percentages 


216  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

of  chlorine  more  or  less  parallel  to  the  coast-line.  This  has  been 
done  by  the  chemists  of  the  Metropolitan  Water  Commission  of 
Massachusetts  and  elsewhere. 

The  action  of  chlorine  on  lead  is  not  very  rapid,  but  many 
acid  substances  act  more  violently,  and  so  far  as  my  own  rather 
extensive  observations  have  gone,  red-lead  paint  is  never  used 
about  chemical  works,  smelters,  etc.,  where  better  results  are  had 
by  the  use  of  varnish  or  a  varnish  paint. 

Unreliable  Reports. — Actual  use  on  a  large  scale  is  the  best 
test  of  a  paint,  but  it  is  very  difficult  to  be  sure  of  your  conclu- 
sions even  from  such  use.  The  chief  metal  structures  which 
are  accessible  for  observation  are  bridges.  A  competent  man 
who  should  have  charge  of  the  painting  of  a  large  number  of 
these  ought  to  be  able  to  arrive  at  valuable  results,  but  men 
capable  of  making  critical  study  of  so  difficult  a  matter  are  rare, 
and  are  usually  too  valuable  to  be  put  to  such  work.  Tenure  of 
office  is  often  brief,  as  compared  with  the  long  time  needed  for 
such  investigations,  and  very  often  the  corporation  which  owns 
the  bridge  has  adopted  some  one  paint  as  a  standard  and  this 
seems  to  be  able  to  prevent  a  fair  judgment.  The  men  who  are 
in  charge  become  prejudiced  in  favor  of  their  paint  and  can  see 
no  defects  in  it,  and  nothing  good  in  anything  else.  The  very 
workmen  share  in  this  feeling,  and  they  have  learned  how  to 
use  their  standard  paint  to  the  best  advantage,  and  it  is  applied 
better  than  any  other.  They,  in  many  cases,  retouch  wrork 
from  year  to  year,  which  is  quite  right,  but  no  record  of  such 
work  is  made  and  the  bridge  is  reported  as  having  stood  so  many 
years  without  repainting,  while  a  bridge  painted  with  some 
other  material  is  condemned  as  soon  as  it  begins  to  look  shabby* 
The  result  is  that  one  man  who  has  charge  of  the  bridges  for 
one  road  reports  that  a  certain  paint  is  satisfactory  and  better 
than  any  other,  while  the  next  man  on  a  parallel  road  condemns 
the  first  man's  paint  and  extols  a  paint  which  the  other  found 
wanting.  Both  mean  to  be  right;  neither  is  capable  of  knowing 
the  truth.  Nothing  is  more  natural  than  the  desire  to  think 
well  of  one's  own  work,  and  in  practice  I  would  commonly  prefer 


PROCTETION   OF  METALS  AGAINST  CORROSION.       217 

the  real  opinion,  if  it  can  be  got  at,  of  a  paint  manufacturer  to  that 
of  a  user,  for  the  former  has  every  incentive  to  find  out  the  truth; 
the  trouble  with  him  is  that  he  is  disposed  to  think,  and  especially 
to  speak,  most  favorably  of  the  thing  which  sells  the  best.  There 
isn't  much  money  in  being  a  missionary  or  a  reformer.  Sell 
people  what  they  think  they  want,  not  what  you  think  they  ought 
to  want,  is  the  business  maxim;  and  this  feeling  interferes  with 
testing  paint  or  anything  else. 

Paint  Tests. — Paint  may  also  be  tested  with  sets  of  test-plates. 
If  such  experiments  are  made  with  sufficient  care  they  are  valu- 
able, and  as  matters  actually  stand,  this  is  the  most  available 
way  of  getting  reliable  results.     But  it  is  not  an  easy  or  simple 
thing  to  get  at  the  truth  in  this  way.     I  would  say  in  the  first 
place  that  the  plates  should  not  be  too  small.     I  have  myself 
used  plates  measuring   twelve  inches  by   twenty,   and  I   think 
they  would  be  better  if  they  were  larger.     They  should  not  be 
of  thin  metal,  never  by  any  chance  of  sheet  iron,  but  thick  enough 
so  that  they  will  not  bend  or  spring  under  any  pressure  which 
is  likely  to  be  applied  to  them.     They  should  be  of  pickled  and 
cold-rolled  steel,  unless  a  test  of  the  behavior  of  paint  on  other 
metal  is  in  question,  and  perfectly  free  from  scale  and  rust;   all 
exactly  alike  in  these  regards.     I  mark  plates  with  a  steel  num- 
bering stamp  on  the  middle  of  each  side  and  also  mark  the  same 
plates  with  a  series  of  saw-nicks  on  one  edge;    these  latter  are 
perfectly  reliable  and  easy  to  find;    the  former  are  more  easily 
read  and  sufficient  in  most  cases.     The  paint  or  varnish  used 
should  be  in  its  best  condition  and  applied  under  favorable  con- 
ditions of  temperature  and  weather  and  after  each  coat  the  plate 
should  be  hung  up  to  dry  for  at  least  a  month.     To  facilitate 
hanging  up  these  plates  a  hole  should  be  bored  in  each  end  of  the 
plate,  about  half  an  inch  in  diameter,  and  the  plate  should  be 
hung  alternately  from  these  holes  as  alternate  coats  are  applied. 
For  the  reasons  already  given  it  is  necessary  to  apply  a  striping 
coat  along  the  margins  of  the  plates  between  the  first  and  second 
coats,  and  if  three  coats  are  applied  it  would  be  well  to  apply  a 
second  striping  coat  between  the  second  and  third  or  else  after 


218  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

the  third;  this  I  have  not  myself  practised,  usually  making  two 
•coat  tests;  the  striping  coat  requires  thorough  diying.  Unless 
the  test  is  simply  a  weathering  test,  the  plates  should  be  hung 
up  in  a  room  where  the  air  is  ordinarily  pure  and  dry  for  six 
months  after  the  painting  is  completed  before  the  test  begins; 
but  if  they  are  to  be  used  in  a  weathering  test,  they  may  be  ex- 
posed as  soon  as  they  are  reasonably  dry  and  it  is  certain  that 
all  are  in  about  the  same  condition.  It  is  very  desirable  that 
the  thickness  of  each  plate  should  be  measured  with  a  vernier 
•caliper  before  painting  at  certain  designated  spots;  for  example, 
the  caliper  may  be  applied  at  a  point  il  inches  back  from  the  edge 
and  4  inches  to  the  right  of  each  corner.  Record  is  made  of  these 
measurements,  and  when  the  last  coat  of  paint  is  dry  the  thick- 
ness may  be  again  measured;  if  the  plate  is  painted  on  both 
.sides,  which  I  think  is  the  better  way,  the  difference  in  measure- 
ment, divided  by  two,  gives  the  thickness  of  the  paint-  or 
•varnish-film. 

Electrical  Tests. — If  the  caliper  can  be  depended  on  to  read 
the  ten-thousandths  of  an  inch  this  measurement  will  be  impor- 
tant, especially  if  the  porosity  of  the  coating  is  to  be  determined 
by  its  electrical  insulating  power.  If  this  test  is  made  it  must 
be  remembered  that  the  ease  of  insulation  varies  with  the  square 
of  the  thickness  of  the  coating,  and  that  only  the  direct  current 
Is  to  be  used,  because  with  the  alternating  current  there  is  danger 
that  the  plate  will  act  as  a  condenser  and  conceal  the  real  voltage. 
Such  electrical  tests  if  made  at  different  periods  during  the  time 
test  will  be  of  much  interest;  so  far  as  I  know  this  has  never 
been  done.  Coatings  for  special  uses  should,  of  course,  be 
tested  after  being  applied  in  the  way  which  is  best  suited  to  de- 
velop their  possibilities;  if,  for  example,  we  are  to  test  a  baked 
coating  against  an  ordinary  paint  or  varnish,  we  should  bake  it 
under  favorable  conditions,  but  we  would  not  therefore  bake 
the  competing  preparations,  which  should  be  applied  in  the 
usual  manner. 

Protect  Edges. — In  any  method  of  exposing  plates  which  I 
liave  ever  seen,  it  is  impossible  to  avoid  injury  to  the  edges  of 


PROTECTION  OF  METALS  AGAINST  CORROSION.        219 

the  plates,  and  as  the  marginal  portion  of  a  plate  of  ordinary 
size  is  a  large  proportion  of  its  total  surface,  we  should  either 
start  out  by  saying  that  we  will  not  count  as  part  of  the  test  the 
strip,  say  an  inch  or  an  inch  and  a  half  wide,  along  the  edge  of 
any  plate,  or  we  should  take  some  extraordinary  measures  to 
prevent  such  injury.  This  is  especially  important  with  plates 
immersed  in  the  water,  which  are  often  injured  more  by  floating 
objects  carried  by  tides  and  currents,  perhaps  far  below  the 
surface  (ice,  for  example),  which  because  of  their  weight  and 
rigidity  strike  severe  blows  and  thus  mechanically  remove  the 
coating,  no  matter  how  firm  it  may  be.  I  have  thought  that 
it  might  be  a  good  plan  to  set  each  plate  in  a  wooden  frame, 
like  those  on  the  slates  of  school  children;  these  would  give 
considerable  protection.  I  have  not  known  this  to  be  done, 
but  I  see  no  objection  to  it.  This  danger  of  marginal  injury 
is  one  of  the  most  serious  objections  to  plate  tests. 

A  most  serious  matter  is  the  difficulty  of  knowing  that  the 
plates  are  all  alike.  When  a  coating  for  any  reason  begins  to 
fail,  and  even  when  perfectly  new,  if  it  is,  like  almost  all  coatings, 
a  little  porous,  it  is  obvious  that  if  we  have  two  plates  coated 
exactly  alike,  and  the  metal  of  one  is  more  easily  corroded  than 
the  metal  of  the  other,  the  coating  on  the  former  plate  will  appear 
to  perish  sooner  than  on  the  latter.  Chemical  tests  will,  of  course, 
show  differences  of  composition  if  there  are  any,  but  I  do  not 
think  it  very  difficult  to  get  plates  of  the  same  chemical  compo- 
sition, but  the  physical  or  molecular  structure  has  great  influence, 
and  I  do  not  know  how  to  determine  this  condition.  That  its 
effect  is  real  is  shown  by  the  following  facts :  Copper  pipe  is  used 
on  the  ships  of  our  navy  for  fire  mains  and  other  purposes;  this 
is  made  in  sections  with  flanged  ends.  The  flange  is  made  by 
slipping  over  the  end  of  the  pipe  a  tightly  fitting  brass  ring,  and 
the  projecting  end  of  the  copper  pipe  is  expanded  by  hammering, 
so  that  the  ring  cannot  come  off.  This  hammering,  of  course, 
draws  out  the  copper  and  disturbs  its  structure  without  affecting 
its  chemical  composition;  as  the  pipe  is  composed  of  copper,  as 
nearly  chemically  pure  as  can  be  commercially  obtained,  there 


220  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

may  be  said  to  be  no  chemical  difference  in  its  different  parts. 
These  sections  of  pipe  were  coated  with  a  varnish  enamel  all 
alike. 

Influence  of  Molecular  Structure. — After  prolonged  use  it  was 
found  that  the  coating  was  in  good  condition  except  near  the 
flanges,  where  the  metal,  though  it  had  not  been  actually  ham- 
mered, had  been  drawn  by  the  blows  on  the  adjacent  ends.  This 
occurred  not  in  one  but  uniformly  in  very  many  instances,  so  that 
the  inference  that  the  liability  of  corrosion  of  the  copper  is  de- 
pendent on  its  molecular  structure  was  unavoidable.  If  this  is 
true  of  copper,  it  is  probably  true  of  steel  and  iron ;  and  the  effect, 
instead  of  being  inconsiderable,  is  very  marked.  It  is  easy  to 
see  that  differences  in  temperature  while  rolling  steel  plate  or 
bars  may  make  difference  in  structure,  as  do  also  differences  of 
thicknesses  or  section.  This  is,  in  fact,  well  known,  for  a  steel 
wire  is  three  times  as  strong  as  the  same  metal  rolled  into  a  bar. 
It  is  then  possible  that  two  test-plates  which  look  alike  may  vary 
by  an  important  amount  in  resistance  to  corrosion,  and  this  at 
once  introduces  uncertainty  into  the  most  carefully  conducted  test. 
This  is,  in  fact,  a  valid  objection,  so  far  as  it  goes,  to  ail  test-plate 
experiments;  yet  the  practical  difficulties  of  getting  fair  experi- 
ments made  on  a  large  scale  are  probably  vastly  greater. 

The  foregoing  discussion  of  the  way  to  conduct  tests  is  pre- 
liminary to  the  following  account  of  some  tests  made  by  the  author, 
which  will  be  followed  by  some  remarks  on  varnishes  and  var- 
nish paints,  as  used  for  the  protection  of  structural  metal.  The 
substance  of  these  experiments  has  already  been  published  in  the 
Transactions  of  the  American  Society  of  Civil  Engineers,  but  it 
is  worth  while  to  bring  together  the  whole  in  a  somewhat  more 
connected  form. 

In  1895  I  had  eighty- four  plates  prepared  for  a  test  in  sea- 
water.  Permission  was  ob tamed  from  the  U.  S.  Navy  Depart- 
ment to  make  use  of  the  facilities  of  the  New  York  Navy  Yard, 
and  I  was  especially  fortunate  in  having  the  cordial  assistance  and 
co-operation  of  Naval  Constructor  F.  T.  Bowles  (afterward  Chief 
Constructor  and  Rear  Admiral),  in  carrying  out  the  work  after 


PROTECTION  OF  METALS  AQAINST  CORROSION.       221 

the  plates  had  been  made  ready.  The  plates  were  coated  at  the 
works  of  Edward  Smith  &  Co.,  who,  moreover,  paid  the  ex- 
penses of  this  and  the  following  series  of  tests,  the  most  extensive 
and  I  believe  the  most  important  that  have  been  made  up  to  the 
present  time.  Thirty  of  these  plates  were  of  aluminum,  and 
were  furnished  without  cost  by  the  Pittsburgh  Reduction  Com- 
pany, makers  of  aluminum.  Prior  to  this  time  aluminum  had 
been  used  in  marine  work  and  had  been  condemned,  as  the  sea- 
water  attacked  and  dissolved  it,  but  pure  aluminum  had  not  been 
used,  and  it  was  desirable  to  know  whether  the  pure  metal  or 
some  alloy  of  known  composition  might  not  be  available,  and 
also,  of  course,  what  coating  was  best  for  its  protection.  Five 
series  of  aluminum  plates  and  alloys  were  provided,  ranging  from 
75  per  cent,  aluminum  to  994  per  cent.,  which  was  at  the  time  the 
purest  aluminum  which  could  be  commercially  prepared.  There 
were  six  plates  in  each  series  and  a  corresponding  number  of 
varnish  coatings  were  applied,  so  that  each  of  these  coating  com- 
pounds was  applied  to  one  of  each  of  the  different  kinds  of  alu- 
minum plates.  In  this  way  the  different  alloys  could  be  com- 
pared and  so  could  the  different  coatings.  The  same  coatings 
were  applied  to  some  of  the  steel  plates,  but  the  greater  number 
of  the  latter,  and  the  fact  that  they  were  all  of  one  metal,  made  it 
possible  to  use  a  much  greater  number  of  coatings.  The  gen- 
eral plan,  which  was  carried  out  more  fully  in  the  later  set  of 
tests,  was  to  determine  the  comparative  value  of  pure  linseed-oil 
as  a  vehicle,  then  of  a  varnish  containing  a  maximum  proportion 
of  oil  to  the  unit  amount  of  resin,  then  a  medium  varnish,  then 
one  having  a  minimum  proportion  of  oil;  and  as  different  resins 
may  have  varying  values,  to  duplicate  and  in  fact  to  triplicate  those 
varnish  experiments  with  varnishes  made  of  resins  of  three  dif- 
ferent classes.  The  resins  selected  were  Zanzibar,  Kauri,  and 
Manila.  The  latter  is  said  to  be  a  "recent"  resin,  that  is,  one 
taken  from  the  living  tree ;  Kauri  is  a  semi-fossil  resin,  from  trees 
of  a  species  now  living,  but  of  no  use  except  as  it  has  lain  buried 
in  the  ground  for  a  long  time  and  undergone  chemical  change ,- 
while  Zanzibar  is  a  fossil  so  old  that  the  trees  themselves  have 


222  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

become  extinct.  The  three  resins  are  well  known  and  are  com- 
monly regarded  as  types  of  the  classes  to  which  they  belong. 
Besides  these  there  were  a  few  special  paints  or  compounds  tried, 
red  lead  and  oil  being  one,  and  another  the  baked  enamel  known 
as  the  "Sabin  Coating,"  which  will  be  more  particularly  men- 
tioned in  describing  the  coating  of  pipes;  also  a  special  oleo- 
resinous  varnish  known  by  the  trade  name  of  Durable  Metal  Coat- 
ing, in  which  a  certain  amount  of  gilsonite  replaces  a  correspond- 
ing amount  of  vegetable  resin.  It  is  interesting  to  note  that  a 
varnish  of  very  similar  composition  to  this  was  used  in  the  first 
really  scientific  sea-water  tests  of  which  I  can  find  any  record, 
t)y  Mr.  Robert  Mallet,  who  made  reports  to  the  British  Asso- 
ciation for  the  Advancement  of  Science  in  1838,  1842,  and  1843; 
and  such  a  varnish,  with  one  other  made  entirely  from  fossil 
resins  and  containing  a  large  amount  of  oil,  were  the  best  of  all 
the  different  paints  and  coatings  which  he  tried.  His  exposures 
were  for  a  period  of  eighteen  months  and  are  worthy  of  study  by 
any  one  interested  in  the  subject.  He  was  handicapped  by  lack 
of  knowledge  of  the  art  of  making  varnish  and  paint,  and  of  their 
practical  use,  but  he  approached  the  subject  with  a  truly  scien- 
tific spirit,  and  without  unreasonable  prejudice  or  interest.  The 
aluminum  plates  were  put  in  a  cage  or  framework  by  themselves; 
the  steel  plates  in  two  similar  cages.  Each  cage  or  frame  con- 
sisted of  four  corner-posts  each  about  3  ins.  square  and  4  or  5  ft. 
long;  these  were  mortised  into  2-in.  plank  ends  which  were  about 
2^  ft.  square,  and  the  tenons  were  held  in  place  by  wooden  pins. 
Each  of  these  corner-posts  had  grooves  about  f  in.  deep  and  wide 
enough  to  receive  the  edge  of  a  plate  cut  across  one  side  every 
2  ins.,  and  these  posts  were  so  set  that  the  plates  could  be  slipped 
into  these  grooves  like  shelves,  a  couple  of  inches  apart.  In  this 
way  thirty  plates  would  fill  a  frame  60  ins.  long.  After  the  plates 
were  all  in  place  they  were  prevented  from  sliding  out  by  fixing 
a  bar  across  each  end  of  the  set  of  plates  parallel  with  the  corner- 
posts,  and  the  plates  were  moreover  made  tight  in  the  grooves  by 
little  wooden  wedges  at  each  corner  of  each  plate.  It  was  not 
desirable  to  use  any  metal  about  the  frames,  for  iron  would  rust 


PROTECTION  OF  METALS  AGAINST  CORROSION.       22$ 

out  and  there  was  danger  that  the  vicinity  of  any  other  metal 
might  induce  galvanic  action.  These  frames,  when  filled,  were 
heavy  and  rather  awkward  to  handle.  They  were  suspended  by 
substantial  iron  chains  which  went  entirely  around  each  cage 
lengthwise.  The  iron  rods  from  which  the  links  of  these  chains 
were  made  were  f  in.  in  diameter,  and  so  severe  was  the  corrosion 
that  in  some  cases  these  chains,  of  which  two  were  attached  to  each 
cage,  were  entirely  rusted  away,  although  the  chains  were  "  gal- 
vanized" or  zinc-coated;  and  in  consequence  some  of  the  plates 
were  lost.  In  the  first  test  fourteen  steel  plates  were  lost,  as  is 
shown  by  the  table.  This  first  set  of  plates  was  put  in  the  water 
in  January,  1896,  and  was  taken  out  July  29,  1896,  after  six 
months'  immersion.  During  this  time  they  were  suspended  5, 
or  6  feet  below  the  level  of  the  water,  in  the  New  York  Navy 
Yard,  in  Brooklyn.  The  water  here  is  foul  because  of  the  dis- 
charge of  sewerage  from  the  city,  and  the  conditions  are  more  un- 
favorable than  they  would  be  in  the  water  of  the  open  sea.  The 
strong  tide  constantly  stirs  up  the  mud  from  the  bottom.  When 
the  plates  were  finally  removed  for  examination  it  was  done  in 
the  presence  of  the  Naval  Constructor  and  of  several  well-known 
engineers  and  of  representatives  of  the  technical  press.  The 
reports  in  the  following  tables  are  substantially  those  made  by 
the  combined  inspection  of  these  authorities.  It  has  been  said 
that  the  ends  of  the  frames  in  which  the  plates  were  suspended 
were  of  solid  wood.  After  soaking  in  the  water  these  ends 
swelled,  thus  separating  the  corner-posts  more  than  they  were  at 
first,  and  in  consequence  the  plates  became  loose.  This  caused 
considerable  damage  to  the  coatings  at  the  corners  where  they 
were  in  the  grooves,  and  the  edges  of  the  plates  also  suffered  from 
abrasion  by  objects  floating  in  the  water.  This,  as  has  been 
already  explained,  is  a  serious  cause  of  error,  or  at  least  made  it 
difficult  to  arrive  at  just  conclusions.  Four-fifths  of  all  the  cor- 
rosion occurred  along  this  marginal  strip. 

Among  the  pigments  mentioned  is  one  called  by  a  trade  name 
"Flamingo  Red."  This  was  included,  although  its  composition 
was  unknown,  but  consists  in  considerable  part  of  a  red  coloring- 


224  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

matter  derived  from  coal-tar,  and  it  had  seemed  very  permanent 
in  the  air.  It  did  not  prove  to  be  of  much  value  in  these  tests.  It 
will  be  noted  that  some  of  the  aluminum  plates  are  said  to  have 
"one  side  baked"  and  that  the  steel  plates  are  mostly  made  up 
in  pairs  in  this  first  test.  Of  each  of  these  pairs  one  plate  was 
baked  at  a  temperature  of  215°  to  240°  F.  for  four  hours  or 
longer.  The  steel  plates  bearing  the  odd  numbers  were  dried 
.slowly  at  the  ordinary  temperature  and  the  ones  with  the  even 
numbers  were  baked.  This  was  done  because  it  was  thought 
possible  that  baking  might  add  to  the  durability  of  the  coatings, 
but  the  result  showed  that  while  a  special  coating  made  to  be 
baked  on  was  durable,  the  baking  of  coatings  not  designed  to 
stand  a  high  temperature  was  on  the  whole  injurious  to  them, 
more  so  to  those  which  were  naturally  hard  and  brittle  than  to 
those  which  were  more  elastic.  One  very  remarkable  thing  was 
observed,  in  this  and  the  following  tests,  which  can  hardly  be 
made  to  appear  properly  in  a  tabulated  report  or  indeed  in  any 
kind  of  a  report,  which  is  that  all  these  paints  and  varnishes 
(except  the  "Sabin  Coating,"  which  was  baked  on  at  400° 
F.,  and  thus  stands  apart  from  the  others)  soften  when  soaked 
for  a  very  long  time  in  water.  They  do  not  seem  to  dissolve,  and 
in  many  cases  the  water  does  not  penetrate  to  the  underlying 
metal,  but  the  coating  becomes  soft,  and  though  it  remains  elastic 
it  can  be  scraped  off  in  large  strips.  If,  however,  it  is  not  dis- 
turbed and  the  plate  is  set  up  in  the  air  it  will  dry  out  and  the 
Tarnish  will  become  hard  again  and  even  lustrous.  When  it  is 
soft  it  can  be  scraped  off  with  the  greatest  ease,  and  this  prevents 
its  being  useful  for  submarine  work.  Some  of  the  varnish  enam- 
els were  much  less  affected  in  this  way  than  the  varnishes  them- 
selves, but  none  were  very  resistant.  It  is  obvious,  however, 
that  these  same  coatings  might  give  satisfaction  in  places  where 
they  would  be  dry  part  of  the  time. 

In  the  following  table  the  letter  "K"  stands  for  Kauri  (resin), 
"Z"  for  Zanzibar,  and  "M"  for  Manila,  and  the  numerals  pre- 
fixed to  these  letters  indicate  the  number  of  gallons  of  linseed-oil 
which  are  combined  with  the  unit  amount,  100  Ibs.,  of  resin 


PROTECTION  OF  METALS  AGAINST  CORROSION.       225 


SERIES  I. 

Ninety-nine  and  One-half 
Per  Cent.  Pure  A1ni"i""11* 


SERIES  II. 

Ninety-eight  Per  Cent. 

Aluminum  and  Two  Per 

Cent.  Copper. 


S&  Din    Process 


PCTlGCt* 


Perfect. 


107. 


'Durable     Metal    Coating," 
MM  s:i-  bated. 


102. 

ie.perfect. 
Unbaked  side,  three  blisters, 
i  in.  diameter.  No  gen- 
eral corrosion  or  roughen- 
ing. The  surface  of  the 
paint  had  lost  its  gloss. 
Coating  good  on  edges  of 


108. 
Baked  side,  one  blister,  I  in. 

Unbaked  side,  perfect. 


Ultramarine  Blue,  one  side, 

"Flamingo  Red,"  one  side,  in 

20  K.  varnish,  not  baked. 


Blue.  103. 

Scarcely  any  corrosion,  but 
shows  roughening  of  coat- 
pin- 


Red. 

General  condition  good  ex- 
cept near  edges  of  plate; 
there,  busters  on  surface  i 
in.  wide  along  one-fifth  the 
margin.  Very  little  corro- 
sion. 


109. 

Blue  and  red  about  the  same 
as  103,  except  that  about 
twice  as  much  surface  was 
blistered.  General  condi- 
tion good. 


'White  zinc  in  20  K.  varnish, 
one  side  baked. 


104. 

Baked  side,  about  2  sq.  ins. 
in  one  place  half  covered 
with  small  blisters.  No 


Unbaked  side,  first-rate  con- 
dition. 


Baked  side  badly  blistered  in 
spots  along  the  edges,  a- 
mounting  to  about  6  per 
cent,  of  the  total  surface  of 
the  plate.  Some  corrosion 
under  these. 

Unbaked  side  all  right  except 
that  i  per  cent,  of  the  sur- 
face showed  pin-head  blis- 
ters on  a  strip  about  }  in. 
wide  on  one  edge  of  plate. 


oxide,   in    20    K 
varnish,  one  side  baked. 


105. 

Baked  side,  one  blister  i  in. 
by  $  in.,  otherwise  first- 
rate.  No  corrosion. 

Unbaked  side,  perfect. 


in. 

Baked  side,  four  central  \  in. 
blisters,  numerous  margi- 
nal ones  about  i  £  per  cent, 
of  plate.  Very  httle  corro- 


Unbaked  side,  first-rate  con- 
dition. 


Spar  varnish,  no  pigment,  one 
ade  baked. 


Meet 


106. 


Baked  side,  two  central  blis- 
ters, 2  and  4  sq.  ins.  and 
nearly  all  the  margin  $  in. 
wide.  Considerable  corro- 
sion. Perfect  except  where 
blistered,  lustre  good,  etc. 

Unbaked  side,  two  central 
blisters,  }  sq.  in.  and  i  sq. 
in.,  slight  marginal  corro- 
sion, coating  evidently  thin 
on  edges. 


226 


TECHNOLOGY  OF  PAINT  AND    VARNISH. 


SERIES  III. 
Ninety-eight  Per  Cent.  Alu- 
minum.    (The  quality 
known  in  1895  as  com- 
mercially pure  aluminum.) 

SERIES  IV. 
Ninety-three  Per  Cent.  Alu- 
minum, Seven  Per  Cent. 
Copper. 

SERIES  V. 
Seventy-five  Per  Cent.  Alu- 
minum, Twenty  Per  Cent. 
Zinc,  Three  Per  Cent.  Cop- 
per, One  Per  Cent.  Iron. 

113. 

At  one  corner  a  break  in  the 
coating  let    in  water  and 
caused  a  blister  of  about  2 
sq.  ins.  Coating  rather  over- 
baked  and  brittle,  but  else- 
where perfect. 

Coating  overbaked,  cracked 
at  corners  by  the  wooden 
framework,  and  the   sea- 
water  made  blisters  at  the 
corners,    some    of    which 
were  3  sq.  ins.    Remainder 
of  plate  perfect. 

Coating  overbaked  and  brit- 
tle;   badly   blistered  along 
the  edges.     All  blisters  un- 
der pipe-coating  enamel  are 
continuous  and  start  from 
the  edge.      The  middle  of 
the  plate  was  all  right. 

114. 
Baked  side  perfect. 
Unbaked  side  tough  and  ad- 
herent,   except    one    small 
spot  near  the  middle  of  the 
late  ,  which  looked  as  if  the 
coating  had  been  broken, 
and   where    corrosion    had 
begun. 

120. 

Baked  side  showed  three  blis- 
ters of  about  i  sq.  in.  each, 
and  some  corrosion  under 
these;   otherwise  all  right. 
Unbaked  side  perfect. 

126. 
Baked    side    badly    blistered 
along  the  edge,  6  or  8  per 
cent,  affected. 
Unbaked    side    slightly    blis- 
tered along  one  edge  :    con- 
dition otherwise  good.     No. 
corrosion. 

us- 

Blue    and   red    about    alike. 
No    decided    blisters,    but 
coating  itself  showed  some 
signs  of  decomposition,  es- 
pecially the  blue,  which  had 
a  rough  surface. 

121. 

Blue  and    red  about    alike; 
about  30  per  cent,  blistered 
and  corroded. 

1  27. 

Blue,  considerably   blistered 
along    the    edges,    mainly 
pin-head  blisters.        Little 
corrosion. 
Red,    about    the    same    but 
some  large  marginal  blis- 
ters.   The  red  had  a  smooth 
surface  but  the  blue  was 
rough. 

1  1  6. 
Both  sides  in  good  condition, 
but  showed  some  signs  of 
incipient    blistering    about 
the  edges. 

122. 

Pin-head  blisters  along  the 
edges  ;     general   condition 
all  right. 

128. 
Baked  side,  nine  or  ten  blis- 
ters of  about  i£  ins.  diam- 
eter and  considerable  cor- 
rosion;   remainder  of  sur- 
face good. 
Unbaked  side,  i  per  cent,  of 
the  surface  near  the  edges, 
with  small  blisters  showing 
some  corrosion  :   the  rest  of 
the  surface  all  right. 

117. 
Perfect. 

123. 
Baked  side  all  right. 
Unbaked  side,  seven  or  eight 
small  blisters  but  no   cor- 
rosion.   General  condition 
good. 

1  29. 
Baked  side,  a  large  number  of 
groups  (about  i  in.  diam- 
eter) of  small  blisters  with 
some  corrosion;   the  rest  of 
the  surface  all  right. 
Unbaked     side,     much     the 
same,  not  as  bad. 

118. 
Perfect. 

124. 
Both    sides   badly   blistered 
and    corroded    along    the 
edge,  about   10  per  cent, 
of  the  surface.    Where  not 
blistered  all  right. 

130. 

About  like  1  24. 

PROTECTION  OF  METALS  AGAINST  CORROSION.        227 

weighed  before  melting.  For  example,  20  K.  means  an  oleo- 
resinous  varnish  made  by  melting  100  Ibs.  of  Kauri  resin  and 
combining  with  it  20  gals.,  or  154  Ibs.,  of  linseed-oil.  The  com- 
pound was  subsequently  thinned  with  a  suitable  amount  of  spirit 
of  turpentine,  but  as  this  is  volatile,  no  mention  is  made  of  that  in 
the  abbreviation. 

The  result  of  this  test  was  of  so  much  interest  that  other  plates 
ivere  prepared  and  coated.  About  three  hundred  plates  were  pre- 
pared and  the  time  of  preparation  was  nearly  a  year,  so  that  it 
was  late  in  June,  1897,  before  the  plates  were  in  place  and  the 
exposure  actually  begun.  The  greater  part  of  these  were  steel 
plates  which  were  painted  in  triplicate  sets,  with  the  intention  of 
putting  one  set  in  the  sea-water  in  the  New  York  Navy  Yard, 
one  set  in  the  Navy  Yard  at  Norfolk,  Va.,  and  a  third  set  in  fresh 
water.  The  place  finally  chosen  for  the  last  was  Lake  Cochituate, 
Mass.,  part  of  the  original  Boston  water-supply. 

Besides  these  there  were  twenty-five  plates  of  aluminum  in 
each  of  the  Navy  Yard  sets,  but  no  aluminum  plates  were  put  in 
the  fresh- water  test  because  it  is  well  known  that  pure  water  does 
not  attack  aluminum.  It  will  be  observed  that  in  the  tables 
already  given  the  steel  plates  are  numbered  from  i  to  40,  and  the 
aluminum  from  101  to  130.  It  was,  therefore,  decided  to  number 
the  aluminum  plates  in  this  experiment  from  151  to  200;  the  steel 
plates  for  the  New  York  Yard  from  201  upward;  for  the  Norfolk 
Yard  from  301  upward,  and  for  the  fresh- water  set  from  401 
upward,  and  this  was  done.  The  aluminum  plates  were  of  two 
sorts,  part  being  commercially  pure  aluminum,  as  pure  as  could 
be  made  in  1896,  and  the  remainder  were  of  aluminum  alloyed 
with  5  per  cent,  of  other  metal.  The  plates  numbered  from  151  to 
163,  inclusive,  in  the  New  York  set  correspond  to  those  numbered 
from  176  to  187,  inclusive,  in  the  Norfolk  set,  and  are  pure  alu- 
minum. Those  numbered  from  164  to  175,  New  York,  correspond 
to  188  to  200,  Norfolk,  and  are  of  the  aluminum  alloy. 

Besides  these  regular  sets  of  plates,  a  cage  containing  twenty- 
four  plates,  part  steel  and  part  aluminum,  which  had  in  1896 
been  exposed  for  six  months  in  the  New  York  Yard  and  are  de- 
scribed in  the  foregoing  tables,  were  again  exposed  in  the  New  York 


228  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

STEEL  PLATES.     1896  TEST. 


White  Zinc. 

White  Zinc. 

White  Zinc. 

White    Zinc    and 
White  Lead. 

8  K.  ii,i2. 

Hard  and  brittle,  very 
few  blisters  or  rust- 
spots.  Outer  coat 
separated  from  the 
under  -  coat  when 
scraped,  leaving  the 
latter  on  the  metal. 

8  Z.              23,  24. 

Poor;     thin,    brittle, 
many  rust-spots. 

12  K.  9,  10. 

No.  9.  A  large  num- 
ber of  pin-hole  rust- 
spots  on  one  side. 
Hard  and  brittle. 
No.    10.  No    rust    or 
blisters,    hard   and 
brittle.     These  not 
easily    scraped    off 
while  wet. 

20  K.  7  8. 

Good;  a  few  small 
rust  -  spots  where 
coating  was  thin, 
near  the  margin  ; 
not  easily  scraped 
off  when  wet.  Coat- 
ing brittle. 

2O   Z.                   21,  22. 

Good  condition,  thin 
and     brittle     near 
the  margin;  could 
be  scraped  off  with 
difficulty  when  wet. 

20  M.  15,  1  6. 

Good  condition,  ex- 
cept where  the 
coating  was  thin 
and  brittle  near 
the  margin,  where 
there  was  some 
rust. 

20  K.                3,  4. 

First-rate    condition  ; 
coating     could     be 
peeled    off   with    a 
knife     when     first 
taken      from      the 
water  ;       afterward 
hardened  again. 

30  K.  5,6. 

Tough  coating,  no 
corrosion,  some 
small  blisters  near 
the  margin  where 
the  coating  was 
very  thin. 

30  Z.            19,  20. 

First-rate  condition, 
tough  and  adher- 
ent ;      not      easily 
scraped   off   when 
wet. 

30  M.            13,  14. 

No.  13.  Poor,  many 
minute  rust-spots. 
No.    14.  Better;    lit- 
tle rust.      Coating 
tough  and  good  on 
both  where  heavy, 
brittle    and    poor 
where  thin. 

set.  Half  of  these  were  lost  by  an  accident  in  the  New  York 
Yard,  but  the  remainder  are  described  in  the  following  table, 
pp.  232-239,  their  numbers  of  course  being  the  same  as  in  the 
table  on  pp.  228,  229.  To  make  them  more  prominent,  they 
are  also  distinguished  by  the  date,  1896,  after  the  number. 

The  sets  of  plates  at  the  Norfolk  Navy  Yard  and  at  Lake  Co- 
chituate  were  left  untouched  until  July,  1899,  a  little  more  than 
two  years,  but  those  in  the  New  York  Yard  were  in  cages  which 
were  suspended  to  a  float  which  was  accidentally  sunk  in  July,  1898, 
and  more  than  half  the  plates  were  lost.  The  remainder,  includ- 
ing part  of  the  1896  plates  just  mentioned,  were  taken  out  July 
21,  1898,  after  an  immersion  of  exactly  thirteen  months.  Besides 
this  loss,  one  cage  or  frame  containing  twenty-five  plates — Nos. 
326-350— was  lost  at  Norfolk  by  the  rusting  away  of  the  heavy 


PROTECTION  OF  METALS  AGAINST  CORROSION.       229 
STEEL  PLATES.     1896  TEST. 


White  Lead. 

Miscellaneous. 

Miscellaneous. 

8  M.             17,18. 

Poor;    coating  badly 
decomposed,     the 
action  taking  place 
from  the  outer  sur- 
face.       Not  much 
corrosion. 
No.    1  8  much  better 
than  No.  17. 

31,32,33,34- 

Durable  Metal  Coating. 
Nos.  31   and  33  all  right  except 
some  blisters  where  the  coat- 
ing was  thin. 
Nos.  32  and  34  not  so  good,  more 
blisters. 
Coating    could    be    scraped    off 
while  wet. 

Oil.                                        40. 

Red  lead  in  linseed-oil. 
A  good  many    small   rust  -spots, 
but  no  general  corrosion.  Coat- 
ing considerably  decomposed; 
could  be  scraped  off  with  diffi- 
culty.    Condition  fair. 

35,36,37,38. 

Sabin  Pipe  Coating. 
All  perfect. 

20  K.                               25,  26. 

Flamingo  red  in  20  K. 
Bad  condition,  many  rust-spots. 

20  K.                        I,  2. 

No.     i.      Good,  first- 
rate  condition. 
No.      2.      Good,   but 
some    small     mar- 
ginal blisters. 

20  K.                               27,  28. 

Ultramarine  in  20  K. 
Not  good;    many  small  blisters, 
not  much  rust. 

Japan.                                     39. 

Ivory-black  ground  in  japan. 
Very  bad;  rusty  all  over. 

20  K.                               29,  30. 

Chromium  oxide  in  20  K. 
Poor;    very   many    small    rust- 
spots. 

galvanized  iron  chains  which  suspended  it,  and  the  loss  of  these 
plates  causes  vacant  places  in  the  table,  so  that,  in  order  to  save 
space,  it  has  been  thought  well  to  put  the  descriptions  of  the 
aluminum  and  the  1896  plates  in  these  otherwise  vacant  spaces. 
If  the  reader  will  bear  this  in  mind,  little  trouble  will  be  found  in 
following  out  the  plan  of  the  table,  the  discrepancies  of  which  are 
caused  by  accidental  losses  of  plates.  No  plates  were  lost  in  the 
Lake  Cochituate  set.  The  cages,  or  frames,  in  which  the  plates 
were  held  were  suspended  in  the  Navy  Yard  by  chains  about  six 
feet  below  the  surface  of  the  water  in  such  a  position  that  the 
plates  were  horizontal.  Barnacles  and  other  marine  organisms 
attach  themselves  to  the  under  side  of  the  plates  and  by  sus- 
pending the  plates  so  that  they  were  horizontal,  we  had  practically 
a  double  test,  one  of  the  lower  sides  covered  with  marine  growth 


230  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

and  another  of  the  upper  sides  which  were  practically  clear. 
There  was  no  considerable  deposit  of  silt  on  the  plates.  In  the 
two  years'  exposure  in  the  Norfolk  Yard  the  action  of  these 
organisms  was  so  severe  as  to  destroy  the  coatings  on  the  under 
sides  of  all  the  plates  with  the  exception  of  those  coated  with  the 
"Sabin  Pipe  Coating,"  which  was  not  affected,  although  oysters 
$  ins.  in  length  were  found  growing  on  it.  When  these  were  re- 
moved the  coating  was  found  to  be  intact.  But  with  this  excep- 
tion it  should  be  remembered  in  looking  over  the  table  that  only 
one  side  of  the  plates  in  the  Norfolk  set  is  described,  the  coatings 
on  the  other  side  being  uniformly  destroyed,  while  in  the  New 
York  and  Lake  Cochituate  sets  both  sides  of  the  plates  are  in- 
cluded in  the  description. 

The  cages  containing  the  plates  which  were  put  in  Lake 
Cochituate  were  laid  on  the  bottom,  which  was  hard  and  smooth, 
about  20  feet  below  the  surface.  The  cages,  or  frames,  naturally 
laid  on  their  sides,  so  that  the  plates  were  vertical.  This  made 
no  difference,  because  fresh-water  organisms  are  rare  and  they 
did  not  attack  the  plates. 

In  this  triplicate  test  the  general  scheme  was  to  apply  to  a 
set  of  four  plates  a  set  of  three  varnishes  containing  respectively 
20,  30,  and  40  gallons  of  oil  per  100  Ibs.  of  resin,  and  raw  linseed- 
oil.  Then  for  another  set  of  four  plates,  these  same  liquids  were 
mixed  by  grinding  with  white  zinc;  another  set  of  four  was 
prepared  with  white  lead;  another  set  with  ultramarine  blue; 
another  with  graphite,  and  so  on.  This  ought  to  show  whether 
one  pigment  is  better  than  another  and  which  vehicle  is  the  best. 
Besides  these,  plates  were  painted  with  pure  red  lead  in  pure 
linseed-oil,  with  two  mixtures  of  red  lead  and  white  zinc,  with 
purple  oxide  of  iron' (crocus),  in  oil,  and  with  "Prince's  Metallic" 
oxide  of  iron,  which  is  a  very  well-known  pigment  consisting  of 
iron  oxide  mixed  with  various  silicates  in  oil. 

Besides  these  coatings  of  known  composition,  two  popular  and 
widely  known  proprietary  paints,  the  Eureka  paint  and  the  graphite 
paint  made  by  the  Detroit  Graphite  Manufacturing  Company,  were 
tried.  The  oil  and  proprietary  paints  were  presumed  to  afford  a 
sort  of  standard  by  which  the  other  coatings  could  be  judged. 


PROTECTION  OF  METALS  AGAINST  CORROSION.       231 

The  coating  material  described  in  the  table  as  "Spar"  is  one 
of  the  well-known  class  of  spar  varnishes  used  for  exterior  and 
marine  work,  and  the  kind  used  was  made  by  Edward  Smith  & 
Company.  The  "  I.  X.  L.  No.  2  "  is  a  well-known  interior  varnish. 
The  substance  indicated  by  the  letters  "D.  M.  C."  is  Edward 
Smith  &  Company's  Durable  Metal  Coating,  and  "S.  P.  C."  is 
Sab  in  Pipe  Coating,  the  same  as  in  the  former  test.  "Para- 
hydric"  is  a  coating  similar  to  Durable  Metal  Coating,  but  con- 
taining less  oil,  which  has  been  used  in  painting  the  interior  of 
water-pipes  and  for  steel  in  interior  construction.  "Keystone" 
is  a  well-known  pigment,  probably  ground  slate,  and  was  used 
to  furnish  a  pigment  composed  of  silicates  for  comparison.  The 
iron  oxide  used  is  the  purest  commercial  sesquinoxide  of  iron, 
containing  over  95  per  cent,  oxide  of  iron.  The  purple  oxide 
of  iron  is  oxide  which  has  been  subjected  to  prolonged  heating 
and  is  supposed  to  be  completely  anhydrous.  The  "iron  oxide 
in  shellac"  mixture  was  prepared  from  a  formula  furnished  by 
Naval  Constructor  Bowles.  The  shellac  is  pure  "D.  C."  shellac 
in  grain  alcohol.  The  paints  known  as  Raht Jen's,  Mclnnes',  and 
Holtzapfel  are  anti-corrosive  and  anti-fouling  ships '-bottom 
paints  and  were  furnished  and  applied  by  the  New  York  Navy 
Yard. 

All  the  paints,  except  those  coated  with  the  Sab  in  Pipe  Coat- 
ing, which  had  two  coats,  received  three  full  coats,  well  dried 
between  coats.  The  red-lead  paint  used  weighed  about  35  Ibs. 
to  the  gallon  and  was  put  in  with  the  plate  in  a  horizontal  position, 
on  the  upper  side  of  the  plate.  After  the  paint  had  set,  the  plate 
was  turned  over  and  the  other  side  was  painted.  The  red  lead 
was  in  this  way  more  perfectly  applied  than  it  probably  can 
ever  be  in  actual  work.  The  nomenclature  and  abbreviations 
in  the  following  table  are  the  same  as  heretofore,  with  the  follow- 
ing additions : 

Um.  Blue  =  Ultramarine  Blue' 

W.  Z.        =  White  Zinc; 

W.  L.        =  White  Lead; 

A.  =  Pure  Aluminum; 

A.  A.        =  Aluminum  Alloy,  95  per  cent. 


232 


TECHNOLOGY  OF  PAINT  AND    VARNISH. 


Lake  Cochituate,  Boston.  | 

401-20  K. 

No  rust  except  where  dam- 
aged along  edges;    many 
very  small  blisters. 

404-20  M. 

Much  rust;    coating  much 
injured. 

407-20  Z. 

Not    much    corrosion,    but 
coating  about  destroyed. 

402-30  K. 
Like  401  ,  not  quite  so  good. 

405-30  M. 

Worse   than    404;     coating 
nearly  destroyed. 

408-30  Z. 

Like  407,  but  considerably 
better. 

403-40  K. 
Like  401. 

406-40  M. 
Not  quite  so  bad  as  405. 

40Q-Spar. 

Like  408,  but  perhaps  a  lit- 
tle better. 

|  Navy  Yard,  Norfolk,  Va.  | 

301-20  K.                             (     304-20  M. 

301  to  310,  coatings  not  destroyed;   all  considerably  in- 
jured ;   blistered  in  small  spots  ;  no  considerable  corro- 
sion;  301  worst;   306  and  309  best;  307-8  not  bad. 

307-20  Z. 

302-30  K. 

305-30  M. 

308-30  Z. 

303-40  K. 

306-40  M. 

3og-Spar. 

|  Navy  Yard,  New  York. 

i  (i8p6)-W.  L.  in  20  K. 

Some     rust     along    edges; 
otherwise  in  good  condi- 
tion. 

16  (i8Q6)-W.  Z.  in  20  M. 

One-fifth  of  one  side  rusted  ; 
all  the  rest  in  good  con- 
dition. 

47  (i8g6)-Spar. 

Coating  firm  and  good;  very 
little  rust. 

2  (i8g6)-W.  L.  in  20  K. 
Like  i. 

1  8  (i8g6)-W.  L.  in  8  M. 

Paint   hard   and    firm;     in 
good  condition. 

35  (i896)-S.  P.  C. 

A  little  corrosion  near  the 
edges  ;  otherwise  all  right. 

20  (i896)-W.  Z.  in  30  Z. 
Good.    No  blisters;  no  rust. 

113  (i8Q6)-S.  P.  C. 

Two  small  blisters;    other- 
wise good. 

22  (i8g6)-W.  Z.  in  20  Z. 

Good.          Some    corrosion 
along  edges. 

PROTECTION  OF  METALS  AGAINST  CORROSION.       233 


4x0-1.  X.  L.  No.  2. 

About  like  407. 

4I3-D.  M.  C. 

Good,  except  where  broken 
and  injured  along  edges. 

41  7-Parahydric. 
Numerous      isolated      rust 
spots  about  i  in.  diam- 
eter;    coating    otherwise 
good. 

Lake  Cochituate,  Boston.  1 

41  1  -Shellac. 

Very  excellent  condition. 

414-0.  M.  C. 
Like  413. 

41  8-Parahydric. 
Like  417. 

4i2-Raw  oil. 

Surface     generally     cor- 
roded;  many  tubercles. 

4I5-D.  M.  C. 
Like  413. 

4i9-Parahydric. 
Like  417. 

4i6-D.  M.  C. 
Like  413. 

42o-Parahydric. 
Like  417. 

310-1.  X.  L.  No.  2. 

3I3-D.  M.  C. 

Many    small     blisters,     in 
outer  coat  chiefly;    very 
little  corrosion. 

3i7-Parahydric. 
Coating  all  on;  no  blisters. 

Navy  Yard,  Norfolk,  Va.  1 

3ii-Shellac. 

Coating    practically    gone  ; 
badly  rusted. 

3I4-D.  M.  C. 
Like  313. 

3  1  8-Parahydric. 
Like  317. 

3i.2-Raw  oil. 

Coating     destroyed;      very 
badly  rusted. 

3I5-D.  M.  C. 
Like  313. 

3i9-Parahydric. 
Like  317. 

3i6-D.  M.  C. 
Like  313. 

32o-Parahydric. 
Like  317. 

124  (i8g6)-Spar,  one  side 
baked. 

Very     few     small     blisters, 
otherwise  perfectly  good. 

105  (i896)-Chromium  ox- 
ide in  20  K.,  one  side 
baked. 
A  few  blisters  :  otherwise  in 
excellent  condition. 

,M 

£ 
1 

'd 

1 

1 

104  (i8p6)-W.  Z.in2oK., 
one  side  baked. 

Like  124. 

122  (i8g6)-W.  Z.  in  20  K., 
one  side  baked. 

Like  122. 

. 

234 


TECHNOLOGY  OF  PAINT  AND    VARNISH. 


Lake  Cochituate,  Boston. 

421-8.  P.  C. 
Perfect,  except  where  coat- 
ing is  in  one  or  two  places 
broken  at  edge  with  cor- 
rosion. 

425-W.  Z.  in  20  K. 

Half  the  surface,  along  the 
edges,  blistered,  with  rust 
underneath. 

428-  W.  Z.  in  20  M. 

Outer  layer  of  coating  near- 
ly destroyed;    under-coat 
good. 

422-8.  P.  C. 
Like  421. 

426-  W.  Z.  in  30  K. 

Much  better  than  425  ;  some 
blisters;  little  corrosion. 

429-  W.  Z.  in  30  M. 

A    few     slight     rust-spots; 
outer  coat  blistered. 

423-8.  P.  C. 
Like  421. 

427-W.  Z.  in  40  K. 

Good  condition  ;  some  blis- 
ters   in    outer    layer    of 
coating;  no  rust. 

430-W.  Z.  in  40  M. 

About  one-fifth  rusted  ;  thin 
rust.        Blistered  ;     outer 
coat  chiefly. 

424-8.  P.  C. 
Like  421. 

i 

^2 

I 

i 

$ 
r 

321-8.  P.  C. 

Perfectly    good    condition. 
See  note  in  text. 

325-W.  Z.  in  20  K. 
Blistered  ;  not  very  good. 

179  A—  I.  X.  L.  No.  2. 
Coating  all  gone. 

322-8.  P.  C. 
Like  321. 

176  A-20  K. 

Three-fourths     of     coating 
destroyed;  thin  rust. 

1  80  A-Spar. 

Two-thirds  of  coating  gone, 
but  one-third  in  the  mid- 
dle perfectly  good. 

323-8.  P.  C. 
Like  321. 

177  A-30  K. 
Like  176. 

181  A-D.  M.  C. 

One-fifth      gone,      one-fifth 
blistered  ;       remainder 
good. 

324-8.  P.  C. 
Like  321. 

178  A-40  K. 
Coating  all  gone. 

182  A-S.  P.  C. 

One-tenth     gone     on     one 
edge;  remainder  all  right. 

154  A-I.  X.  L.  No.  2. 

Varnish  half  gone.       Corro- 
sion not  deep. 

M 

£ 

z 
i) 

2 

151  A-20  K. 

Blistered  along  edges  and 
a    few    spots.       Varnish 
firm.     Little  corrosion. 

155  A-Spar. 

Most  of  the  varnish  soft,  but 
some   not   affected.      Not 
badly  corroded. 

1 
>> 
> 
t 
•g 

152  A-30  K. 

Much  corrosion  ;  some  deep. 
Coating   half    gone;     re- 
mainder firm. 

157  A-D.  M.  C. 

Twenty  per  cent,  blistered 
around  edges.        Coating 
firm;  not  much  corrosion. 

153  A-40  K. 

Badly    corroded;      coating 
nearly  all  destroyed. 

158  A-S.  P.  C. 

Excellent.      Coating  not  in- 
jured,    except    by    acci- 
dent   in    removing    from 
frame. 

PROTECTION   OF  METALS  AGAINST  CORROSION.       235 


43I-W.  Z.  in  20  Z. 

Not  much  rust;    outer  coat 
badly     blistered  ;      under 
coat  slightly  so. 

436-W.  Z.  in  20  K.,  baked. 

Almost  perfect;   still  shows 
glossy  surface  of  varnish. 

439-  W.  Z.  in  20  M.,  baked. 

Good;     coating    brittle    in 
places    and     shows     de- 
terioration. 

Lake  Cochituate,  Boston. 

432-W.  Z.  in  30  Z. 

Better  than  431.  Outer  coat 
blistered. 

437-W.  Z.  in  30  K.,  baked. 
Like  436. 

440-W.  [Z.  in  30  M.,  baked. 
A  little  better  than   439 

433-W.  Z.  in  Spar. 
Like  432. 

438-W.  Z.  in  40  K.,  baked. 
Like  436. 

44I-W.  Z.  in  40  M.,  baked. 
Almost  perfect. 

435-W.  Z.  in  Raw  Oil. 

Four-fifths  of   surface 
badly  rusted;     deep   cor- 
rosion. 

183  A-S.  P.  C. 
Perfectly  good  condition. 

187  A-W.  Z.  in  Spar. 
Like  184. 

191  AA-I.  X.  L.  No.  2. 
Coating  all  gone. 

i 

M 

•1 

o 
^ 

-^ 

i 

i 

184  A-W.  Z.  in  30  K. 

Pine;    no   rusting  nor  blis- 
tering. 

1  88  AA-20  K. 
Coating  all  gone. 

192  AA-Spar. 

Three-quarters   gone  ;     like 
189. 

185  A-W.  Z.  in  40  K. 
Like  184,  but  discolored. 

180  AA-30  K. 

Three-quarters  gone;  small 
patch   in   the  middle   all 
right. 

193  AA-Spar. 
Like  192. 

1  86  A-W.  Z.  in  30  Z. 
Like  184. 

190  AA—  40  K. 
Half  gone;  like  189. 

194  AA-D.  M.  C. 

One-third    badly    blistered 
from    edges  ;     remainder 
good. 

159  A-S.  P.  C. 
Like  158  A. 

163  A-W.  Z.  in  Spar. 

Not  deeply  corroded.    Sev- 
eral large  blisters;    other- 
wise in  good  condition. 

167  AA-I.  X.  L.  No.  2. 

Considerable  blistering  and 
corrosion.   Coating  easily 
scraped  off. 

i 

1 

I 

| 

^ 

1  60  A-W.  Z.  in  30  K. 

Upper  side   perfect;     lower 
side     slightly     blistered. 
Coating  hard. 

164  AA-20  K. 

Badly      corroded;       three- 
fourths    of    the    varnish 
destroyed. 

1  68  AA-Spar. 

Like  167,  but  not  badly  cor- 
roded. 

.  161  A-W.  Z.  in4oK. 

No  blisters;    otherwise  like 
1  60  A. 

165  AA-30  K. 
Like  164  AA. 

162  A-W.  Z.  in  30  Z. 
Like  161  A. 

1  66  AA-40  K. 
Badly    blistered,    but    not 
badly  corroded.    Coating 
on  one  side  firm;   on  the 
other  soft. 

169  AA-D.  M.  C. 

Many  blisters;    very  little 
corrosion  ;     coating   gen- 
erally firm. 

236 


TECHNOLOGY  OF  PAINT  AND    VARNISH. 


J  Lake  Cochituate,  Boston.  1 

442-W.  Z.  in  20  Z.,  baked. 

Nearly  perfect. 

445-W.  L.  in  20  K. 

Very  little  corrosion.  Some 
superficial  blisters. 

449-Um.  Blue  in2o  K. 

Considerable       rust.;         not 
deep;     paint     practically 
destroyed. 

443-W.  Z.  in  30  Z.  baked. 

Excellent;  no  rust;  blisters 
superficial  and  few. 

446-W.  L.  in  30  K. 

Good   condition;     no   rust. 
Some  superficial  blisters. 

450  Um.  Blue  in  30  K. 
A  little  worse  than  449. 

444-W.  Z.  in  Spar,  baked. 
Like  443  .or  better. 

447-W.  L.  in  40  K. 
Like  446. 

45i-Um.  Blue  in  40  K. 
Worse  than  449;  deep  rust. 

%448-W.  L.  in  Raw  Oil. 

Much       deep       corrosion  ; 
about  half  the    plate  in 
good  condition. 

452-Um.  Blue  in  Raw  Oil. 

Like    451;     whole    surface 
rusted. 

i 
jy 

1 

-~ 

•? 
i 

195  AA-W.  Z.  in  30  K. 

Good;    blistered  a  little  on 
the  edges. 

199  AA-S.  P.  C. 

Blistered     a     little     from 
edges  ;        otherwise      all 
right. 

— 

196  AA-W.  Z.  in  40  K. 

Fine,   but   discolored;    like 
185. 

200  AA-S.  P.  C. 
Like  199. 

197  AA-W.  Z.  in  30  Z. 

Fine,  but  blistered  a  little 
along   the  edges. 

3Si-Um.  Blue  in  40  K. 
Nearly  all  gone. 

198  AA-W.  Z.  in  Spar. 
Like  197. 

352-Um.  Blue  in  Raw  Oil. 

Coating     all     gone;      very 
badly  rusted. 

1  Navy  Yard,  New  York. 

170  AA-W.  Z.  in  30  K. 

Very  little  corrosion.     Blis- 
ters amount  to  i  per  cent. 
Coating  good. 

174  AA-S.  P.  C. 
In  perfectly  good  condition. 

171  AA-W.  Z.  in  40  K. 

Good,    but    not    equal    to 
170  AA. 

175  AA-S.  P.  C. 
Like  174. 

172  AA-W.  Z.  in  3°  Z. 

No  corrosion;    no  blisters; 
excellent  condition. 

25i-Um.  Blue  in  40  K. 

Very   many   small   blisters; 
very  little  corrosion. 

173  AA-W.  Z.  in  Spar. 
About  like  172. 

252-Um.  Blue  in  Raw  Oil. 

Uniformly  corroded;   coat- 
ing all  gone. 

PROTECTION  OF  METALS  AGAINST  CORROSION.       237 


453-Graphite  in  20  K. 

Very     good;      some     small 
blisters. 

457-Keystone  in  20  K. 

Good  condition;    no   rust; 
scene  small  blisters. 

46i-Iron  Oxide  in  20  K. 

Very  little  rust;   small  blis- 
ters in  outer  coat. 

o 
I 

8 
» 

I 

454-Graphite  in  30  K. 
Like  45  3. 

458-Keystone  in  30  K. 
Like  457. 

462-Iron  Oxide  in  30  K. 
Better  than  461  ;  no  rust. 

455-Graphite  in  40  K. 
Like  453- 

459-Keystone  in  40  K. 

A  little  rust;    many  small 
superficial  blisters. 

463-Iron  Oxide  in  40  K. 
Like  462. 

456-Graphite  in  Raw  Oil. 

Deeply        and        generally 
rusted;     about  one-tenth 
of  the  paint  still  good. 

46o-Keystone  in  Raw  Oil. 

Badly  and  deeply  rusted; 
patches     of     paint     still 
good. 

464-Iron    Oxide   in    Raw 
Oil. 
Corrosion    deep    and    gen- 
eral;  paint  all  gone. 

353-Graphite  in  20  K. 

Three-quarters  gone;   much 
rust. 

357-Keystone  in  20  K. 

Coating  blistered  and  one- 
quarter  gone. 

36i-Iron  Oxide  in  20  K. 

Pretty    good   condition;   a 
few  blisters. 

Navy  Yard.  Norfolk,  Va. 

354-Graphite  in  30  K. 
Half  gone;  much  rust. 

358-Keystone  in  30  K. 

Blistered,    but    not  de- 
stroyed. 

362-Iron  Oxide  in  30  K. 
Not  quite  as  good  as  361. 

355-Graphite  in  40  K. 
One-quarter  gone. 

359-Keystone  in  40  K. 

Blistered,  but  not  in  bad 
condition. 

363-Iron  Oxide  in  40  K. 
Like  361. 

356-Graphite  in  Raw  Oil. 

Nearly     all     gone;      badly 
rusted. 

36o-Keystone     in      Raw 
Oil. 
All  gone;   badly  rusted. 

364-Iron    Oxide    in  Raw 
Oil. 
Like  360. 

253~Graphite  in  20  K. 

A  few  blisters  ;    very  little 
corrosion. 

257-Keystone  in  20  K. 

No     corrosion  ;      numerous 
very  small  blisters. 

26i-Iron  Oxide  in  20  K. 

Blistered,     but     not    very 
badly.    Not  much  corro- 
sion. 

•a 
£ 
^ 

0> 

£ 

•s 

£ 
>> 

> 

cfl 
g 

254-Graphite  in  30  K. 
Like  253. 

258-Keystone  in  30  K. 
Like  257. 

262-Iron  Oxide  in  30  K. 

Like    261.     Not     deeply 
rusted. 

255-Graphitein  40  K. 

No     corrosion.       Paint     in 
good  condition.     Numer- 
ous very  small  blisters. 

25Q-Keystone  in  40  K. 
Like  257. 

263-Iron  Oxide  in  40  K. 
Like  262. 

256-Graphite  in  Raw  Oil. 

Uniformly  corroded;    coat- 
ing all  gone. 

26o-Keystone  in  Raw  Oil. 

Coating      destroyed      and 
plate  badly  corroded. 

264-Iron   Oxide  in  Raw 
Oil. 
Like  260. 

238 


TECHNOLOGY  OF  PAINT  AND   VARNISH. 


Lake  Cochituate,  Boston. 

465-Red  Lead  in  Raw  Oil. 
Paint    still    tough;     looks 
well.      Blisters  from  the 
bottom  with  slight  cor- 
rosion beneath. 

469-Eureka  Paint. 

General    corrosion  ;     paint 
entirely  destroyed. 

47o-Detroit  Graphite. 

Like  469  ;  paint  nearly  all 
destroyed. 

475-International    Holtz- 
apfel. 
Like  469. 

467-Prince's    Metallic    in 
Raw  Oil. 
About   one-quarter  deeply 
rusted;   paint  practically 
all  gone. 

47  2-Iron  Oxide  in  Shellac 
Mixture. 
Good   condition;     about    2 
per  cent,  rusted. 

477-Red  Lead  and  W.  Z. 
in  Raw  Oil. 
Many       deep       rust-spots; 
about    5    per    cent.;     re- 
mainder good. 

468-Purple  Oxide  in  Raw 
Oil. 
Like  467. 

478-Red  Lead  and  W.  Z. 
in  Raw  Oil. 
Like  477.        Not  nearly  as 
good  as  465. 

.  Navy  Yard,  Norfolk,  Va. 

36s-Red  Lead  in  Raw  Oil. 

Coating    destroyed  ;     plate 
badly  rusted. 

369-Eureka  Paint. 
Like  365. 

374-McInnes'  Paint. 
Like  372. 

37o-Detroit  Graphite. 
Like  365. 

375-International    Holtz- 
apfel. 
Like  365. 

367-Prince's    Metallic    in 
Raw  Oil. 
Like  365. 

372-Iron  Oxide  in  Shellac 
Mixture. 
Paint    destroyed;     general 
but  not  deep  corrosion. 

377-Red  Lead  and  W.  Z. 
in  Raw  Oil. 
Like  365. 

368-Purple  Oxide  in  Raw 
Oil. 
Like  365. 

373-Rahtjen's  Paint. 
Like  365. 

378-Red  Lead  and  W.  Z. 
in  Raw  Oil. 
Like  365. 

Navy  Yard,  New  York. 

265-Red  Lead  in  Raw  Oil. 

Coating    badly    destroyed. 
Considerable  corrosion. 

26g-Eureka  Paint. 
Like  260. 

274-McInnes'  Paint,. 

In  good  condition:    no  bar- 
nacles. 

27o-Detroit  Graphite. 
Like  260. 

275-International     Holtz- 
apfel. 
Paint    badly    gone;     much 
corrosion  ;      many    small 
barnacles. 

267-Prince's    Metallic    in 
Raw  Oil. 
Like  260. 

272-Iron  Oxide  in  Shellac 
Mixture. 
A  few  blisters;    otherwise 
in  good  condition. 

277-Red  Lead  and  W.  Z. 
in  Raw  Oil. 
Coating      thin;       gone      in 
many    places;     consider- 
able corrosion. 

268-Purple  Oxide  in  Raw 
Oil. 
Like  260. 

273-Rahtjen's  Paint. 

Paint  badly  gone;    consid- 
erable    rusting.        Many 
small  barnacles. 

278-Red  Lead  and  W.  Z. 
in  Raw  Oil. 
Like  277. 

PROTECTION   OF  METALS  AGAINST  CORROSION.       239- 


481    20  K     baked 

484—30  M.    baked. 

487-1.  X.  L.  No.  2,  baked. 

Practically    perfect;     coat- 
ing still  glossy. 

Several  deep  spots  of  rust, 
coating  badly  blistered. 

Like  481. 

a 

482-30  K.,  baked. 
Like  481. 

485-30  Z.,  baked. 
Like  481. 

488-Raw  Oil,  baked. 

Badly  and  deeply  rusted. 
Two-fifths  of  the  surface 
good. 

3 

1 

a;  • 

1 

483-40  K.,  baked. 
Like  481. 

486-Spar.  baked. 
Like  481. 

48g-D.  M.  C.,  baked. 

Fine;    a  few  small  blisters 
in  the  outer  coat. 

^ 

'.H 

y 

C 

0) 

M 

a 

,-J 

381-20  K.,  baked. 

Half    of    the    coating    de- 
stroyed;    the   rest   good. 
Not  much  rust. 

384-30  M.,  baked. 
Like  382. 

387-1.  X.  L.  No.  2,  baked. 
Like  386. 

J 

382-30  K.,  baked. 

Four-fifths  destroyed;   very 
little  rust. 

385-30  Z.,  baked. 
Like  382. 

388-Raw  Oil,  baked. 
All  gone;  rusted. 

Norfolk,  V 

383-40  K.,  baked. 
Like  382. 

386-Spar,  baked. 
Nearly  all  gone;  little  rust. 

389-0.  M.  C.,  baked. 

Three-quarters    gone;     re- 
mainder good;  very  little 
rust. 

'H 

a 
> 

t 

d 

'/< 

281-20  K.,  b,aked. 

Plate    thinly    rusted    along 
the  edges. 

284-30  M.,  baked. 

Many  small  and  some  me- 
dium-sized blisters.     Not 
badly  rusted. 

287-1.  X.  L.  No.  2,  baked. 

Not  much  corrosion;    very 
small  blisters. 

282-30  K.,  baked. 

Small    blisters,    with    thin 
rust  beneath,  over  most 
of  the  plate. 

285-30  Z.,  baked. 

Good  condition.  Very  little 
rusting.    Very  small  blis- 
ters. 

288-Raw  Oil,  baked. 

Badly  corroded.       Coating 
destroyed. 

1 
1 

283-40  K.,  baked. 

Very    small    blisters;     not 
much  mst. 

286-Spar,  baked. 

Coating    badly    destroyed; 
much  corrosion. 

28g-D.  M.  C.,  baked. 

Very  many  small  blisters. 
Not    very    much    corro- 
sion. 

I 

>, 

1 

.1240  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

A  careful  study  of  the  plates  after  their  removal  from  the 
ivater  showed  that  it  is  generally  true  of  all  the  better  class  of 
coatings  that  corrosion  begins  at  the  edge  of  the  plate.  In  the 
•case  of  aluminum  plates  it  seemed  evident  to  the  writer  that  some 
of  these  coatings,  notably  the  spar  varnish  and  the  "Durable 
Metal  Coating, "  had  been  gradually  thrown  off  by  corrosion  creep- 
ing from  the  edge,  probably  from  some  mechanical  injury  under 
the  varnish,  a  patch  of  which  remained  uninjured,  elastic,  and 
apparently  without  deterioration  on  the  middle  of  the  plate. 
This  fact  should  not  be  lost  sight  of  in  considering  this  matter, 
and  is  one  of  the  points  shown  by  an  inspection  of  the  plates,  but 
not  brought  out  easily  in  a  description.  As  a  rule,  with  the 
less  effective  coatings,  they  begin  to  deteriorate  from  the  surface, 
which  becomes  rough;  then  little  blisters  appear  which  are 
caused  by  the  separation  of  the  last  coat  from  those  beneath; 
finally  the  undercoat  blisters,  in  which  case  it  is  found  almost 
invariably  that  rust  has  formed  under  the  blister.  If,  however, 
the  coating  is  porous,  and  this  seems  to  be  the  case  with  the 
ordinary  oil  paints,  the  water  reaches  the  metal  and  causes  rust. 
This  throws  off  the  paint-film,  and  the  corrosion  spreads  rapidly 
in  this  way. 

These  tests  undoubtedly  seem  to  prove,  and  I  think  they  do 
prove,  that  varnish  forms  a  much  more  continuous  (less  porous) 
film  than  oil,  which  agrees  with  all  that  has  heretofore  been 
said  of  the  nature  of  varnish-films.  In  all  these  tests  the  oil  paints 
have  failed  without  exception,  while  the  corresponding  varnish 
paints  remained  in  most  cases  in  good  condition.  The  charac- 
ter of  the  pigment  does  not  seem  to  have  much  influence.  All 
the  oil-paint  samples  were  so  badly  rusted  that  differentiation 
among  them  was  impossible.  It  may  be  that  an  earlier  inspec- 
tion would  have  shown  differences,  but  as  it  was,  the  appearance 
of  all  these  plates  when  removed  from  the  water  was  so  similar 
that  it  seems  unlikely,  and  certainly  the  varnish  paints  did  not 
show  any  great  difference  in  the  matter  of  the  pigments,  except 
that  white  zinc  seemed  to  be  somewhat  the  best.  The  iron 
oxides,  graphites,  and  pulverized  slate  were  all  alike.  The  red 
lead,  in  the  Lake  Cochituate  and  New  York  sets,  was  far  better 


PROTECTION  OF  METALS  AGAINST  CORROSION.       241 

than  any  of  the  oil  paints.  The  mixtures  of  red  lead  and  white 
zinc  were  markedly  inferior  to  red  lead  alone.  In  the  Norfolk 
test,  which  was  much  more  severe,  the  red  lead  had  finally  been 
quite  destroyed.  Deterioration  in  the  case  of  red  lead  always 
seems  to  start  from  centres.  In  the  Lake  Cochituate  set  the 
red  lead  was  in  pretty  good  condition,  but  as  it  showed  numerous 
rust-spots,  without  superficial  blisters,  but  all  defects  running 
through  to  the  metal,  it  probably  would  not  have  lasted  more  than 
a  year  or  so  longer.  Most  of  the  varnish  paints  were  much 
better  than  the  red  lead.  A  study  of  the  varnishes  applied  with- 
out pigment  seems  to  show  that  in  the  fresh-water  exposure  the 
process  of  baking  was,  on  the  whole,  of  advantage,  but  not  greatly 
so.  In  the  salt  water  the  unbaked  varnishes  were  better  than 
the  same  varnishes  baked.  This  agrees  with  the  results  of  the 
1896  tests.  The  Manila  varnishes  are  clearly  inferior  to  the 
Kauri  and  Zanzibar.  The  ''Durable  Metal  Coating"  was  best 
of  all.  This  is  doubtless  due,  in  a  large  degree,  to  the  fact  that 
this  varnish,  which  is  intended  especially  for  the  protection  of 
structural  steel,  is  made  with  a  heavy  body  and  the  film  is  of  greater 
thickness  than  is  the  case  with  varnishes  intended  for  woodwork. 
Its  composition  has  also  been  very  carefully  studied  and  designed 
to  secure  great  durability,  which  is  of  much  less  importance 
than  other  qualities  in  ordinary  varnishes. 

By  far  the  best  results,  however,  with  the  exceptions  to  be 
hereafter  noted,  were  obtained  from  the  best  of  the  enamel  paints. 
Here,  also,  the  Manila  varnishes  were  decidedly  inferior,  and  in 
my  opinion  these  should  be  excluded  hereafter  from  any  such 
tests,  although  they  make  a  very  good  showing  on  wood.  In 
the  enamel  or  varnish  paints,  those  made  with  the  more  elastic 
varnishes  (those  containing  the  most  oil)  were  decidedly  the 
better.  The  extreme  durability  of  these  is  well  shown  by  the 
1896  plates.  These  were  first  exposed  to  the  air  two  or  three 
months,  then  they  were  in  the  sea- water  six  months,  then  exposed 
to  the  air  nearly  a  year,  then  under  water  thirteen  months,  and 
have  since  been  exposed  to  the  air  five  years,  making  a  total  of 
eight  years,  and  they  are  still,  to  all  intents,  perfect.  It  is  true 
that  the  air  exposures  have  been  indoors,  but  most  paints  rapidly 


242  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

lose  their  coherence  when,  after  a  prolonged  immersion,  they 
are  exposed  to  the  air.  Two  years'  continuous  submersion  in 
fresh  water  has  not  injured  some  of  these  enamels,  and  two  years 
in  the  excessively  severe  exposure  at  the  Norfolk  Navy  Yard 
has  left  several  of  them  in  good  condition,  a  few  being  practi- 
cally uninjured.  Undoubtedly  the  most  obvious  and  conspicu- 
ous and  the  most  instructive  part  is  the  total  and  absolutely 
universal  failure  of  linseed-oil  films,  either  alone  or  mixed  with 
any  of  the  numerous  pigments  which  were  tried,  while  the  corre- 
sponding varnishes  and  enamel  paints  made  with  the  same  pig- 
ments were  in  fair  to  good  condition.  It  is  not  to  be  forgotten, 
however,  that  the  only  varnishes  used  in  this  test  were  those 
having  20,  30,  and  40  gallons  of  oil  to  the  unit  ioo  Ibs.  of  resin. 
The  30  and  40-gallon  varnishes  may  be  regarded  as  special  struc- 
tural varnishes,  being  more  elastic  and  less  brilliant  and  hard 
than  are  acceptable  for  any  ordinary  commercial  work;  the 
20-gallon  varnishes,  which  made  the  poorest  showing,  being  the 
only  really  commercial  varnishes  in  these  tests,  except  the  spar, 
which  is  intermediate  between  the  twenties  and  thirties,  made 
especially  for  marine  use,  and  the  " Durable  Metal  Coating,"  a 
highly  elastic  special  varnish  made  exclusively  for  structural 
metal  protection.  The  relatively  poor  showing  made  in  1896 
by  the  8-  and  i2-gallon  varnishes  sufficiently  proves  that  the  best 
ordinary  varnishes,  though  made  with  the  highest  skill  and  of  the 
most  expensive  materials,  are  unfit  for  prolonged  and  severe 
exposures.  The  results  which  are  likely  to  be  obtained  from 
the  use  of  common  cheap  varnishes  may  safely  be  left  to  the 
imagination  of  the  reader.  The  great  durability  of  the  varnish 
and  enamel  films  in  these  tests  confirms  strikingly  the  opinion 
long  held  by  the  writer  that  properly  made  varnish-films  are 
much  more  impervious  and  resistant  than  any  others.  The  excep- 
tional cases  to  be  noted  are: 

First.  The  "Sabin  Coating,"  a  baked  enamel,  which  is  so 
much  superior  to  the  others  as  to  form  a  class  by  itself,  and 

Second.  The  extraordinary  showing  made  by  pure  shellac 
varnish  in  the  Lake  Cochituate  test. 


PROTECTION   OF  METALS  AGAINST  CORROSION.        243 

Shellac  Varnish  in  Fresh  Water. — Shellac  varnish  is  simply 
a  solution  of  shellac  resin,  which  is  chemically  an  acid  substance, 
in  alcohol.  There  are  many  grades  of  shellac;  the  one  used 
was  what  has  for  many  years  been  known  as  "D.C."  Orange 
Shellac,  and  it  was  dissolved  in  pure  97  per  cent,  grain  (ethylic) 
alcohol.  Being  an  acid  substance,  it  is  attacked  readily  by  the 
ammonia  in  the  atmosphere.  It  is  removed  easily  by  soap  and 
water.  It  has  never  been  considered  a  durable  varnish  as  ordi- 
narily used  on  woodwork,  and  it  does  not  stand  at  all  in  the  sea- 
water  tests,  but  two  years'  exposure  under  20  feet  of  fresh  water 
does  not  seem  to  have  injured  it  sensibly.  This  may  be  a  serious 
matter,  for  while  in  this  regard  it  is  no  better  than  some  other 
varnishes  which  cost  less  money,  shellac  varnish  has  some  impor- 
tant and  exceedingly  desirable  qualities  which  no  other  varnish 
has.  For  example,  occasionally  we  encounter  the  problem  of 
repainting  a  large  section  of  large  water-pipe  which  can  be 
spared  for  use  only  a  few  days.  The  interior  of  this  pipe  is  damp. 
The  best  that  can  be  done  with  it  is  to  get  out  most  of  the  visible 
water,  but  the  cold  surface  of  the  metal  will  always  be  damp. 
No  ordinary  varnish  will  stick  to  such  a  surface,  and  corrosion 
will  probably  be  set  up  at  once.  No  oleo-resinous  varnish  of 
ordinary  character,  of  sufficient  durability  to  be  worth  putting 
on,  will  dry  in  the  limited  time  at  our  disposal.  But  shellac 
is  dissolved  in  a  vehicle  which  has  an  intense  affinity  for  water, 
and  a  thin  film  of  dew  will  be  instantly  absorbed  and  removed 
by  the  evaporation  of  the  slightly  diluted  alcohol;  and  shellac, 
if  applied  in  a  thin  coat,  dries  with  the  greatest  rapidity.  Three 
coats  may  be  applied  in  eight  to  twelve  hours.  There  is  no 
unpleasant  or  dangerous  odor,  though  ventilation  should  be 
secured  both  on  account  of  the  risk  of  fire  and  because  working 
in  an  atmosphere  of  alcoholic  vapor  produces  intoxication.  It 
certainly  seems  from  this  test  as  though  we  should  be  justified 
in  using  shellac  varnish  in  such  a  case.  It  is  expensive,  of  course, 
and  it  is  almost  certain  that  the  cheaper  grades,  which  are  found  in 
ordinary  use  to  be  very  much  inferior  in  durability,  would  not  be 
so  efficient.  In  any  case,  it  would  not  be  necessary  to  use  it 


244  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

when  the  conditions  are  such  that  some  equally  good  (or  better) 
but  slower-drying  coating  can  be  used. 

During  the  years  which  have  elapsed  since  these  tests  were 
made  the  writer  has  given  considerable  attention  to  the  subject 
of  ships'-bottom  paints,  which  are  all  made  with  a  quick-drying 
spirit  varnish  as  the  vehicle  for  the  first  coat,  and  there  is  no 
doubt  that  these  varnishes  act  as  shellac  acted  in  this  test.  Of 
course  none  of  these  have  as  much  durability,  because  they  are 
in  sea-water  instead  of  fresh  water,  but  they  are,  like  shellac, 
coatings  which  will  not  stand  weather  exposures  for  even  a  few 
months,  but  when  put  under  water  immediately  after  their  appli- 
cation they  last  six  to  twelve  months.  This  is  well-established 
practice,  known  to  all  who  have  the  care  of  ships,  and  strongly 
confirms  the  opinion  just  expressed,  that  the  use  of  shellac  in 
such  a  case  as  has  been  described  could  not  be  regarded  as  an 
unwarranted  experiment. 

It  is  sometimes  objected  to  these  submarine  tests  that  they 
are  of  value  only  as  regards  the  same  conditions,  and  there  is 
some  justice  in  such  a  criticism,  but  it  is  much  weakened  by  the 
obvious  fact  that  there  is  a  practical  agreement  between  the 
fresh-water  and  the  sea-water  tests.  The  latter  were  most  severe, 
but  in  most  cases  the  difference  has  been  one  of  degree  only. 
And  in  the  rather  large  experience  of  the  writer  and  his  asso- 
ciates these  tests  seem  to  agree  in  general  with  aerial  exposures, 
reasonable  exception  being  made  in  the  case  of  coatings  intended 
expressly  for  marine  or  for  aerial  use.  The  zinc  and  lead  enamels 
make  a  rather  better  relative  showing  under  water  than  in 
weather  exposures,  although  excellent  for  the  latter. 

Laboratory  Tests  not  Decisive. — Exposure  tests,  such  as  these, 
are  of  much  more  importance  than  laboratory  tests.  The  manu- 
facturers of  paints  and  varnishes,  some  of  whom  are  probably 
the  best  experts  in  this  matter,  never  depend  on  any  but  an  expo- 
sure test.  It  is  by  no  means  impossible  that  rapid  laboratory 
tests  may  yet  be  devised,  but  such  crude  ones  as  have  been  so 
far  proposed  are  in  most  cases  of  little  value.  Such  a  test,  for 
example,  is  that  with  caustic  alkali.  This  is  a  substance  unknown 


PROTECTION  OF  METALS  AGAINST  CORROSION.       245 

in  nature,  and  no  good  paint  will  stand  it,  while  a  perfectly  worth- 
less paint  may  be  made  which  will  stand  it  very  well.  A  nitric- 
acid  test  is  of  the  same.  sort.  It  will  simply  burn  up  any  organic 
substance,  and  some  of  the  best  linseed- oil  paints  yield  to  it  most 
readily.  It  would  hardly  be  regarded  as  a  fair  test  of  the  com- 
parative health  of  a  dozen  animals  to  administer  to  each  of  them 
a  couple  of  ounces  of  nitric  acid  and  watch  to  see  which  lived 
longest,  yet  probably  each  could  take  a  few  drops  of  it  per  day 
without  inconvenience.  This  is  about  what  many  of  the  so- 
called  paint  tests  amount  to.  Some  laboratory  tests  are  of  some 
value,  but  none  is  conclusive.  A  heat  test  is  at  present  popular. 
The  painted  sample  is  heated  to  perhaps  400°  Fahr.  for  a  time 
and  its  subsequent  appearance  studied,  on  the  supposition  that 
the  rapidly  increased  oxidation  at  high  temperatures  may  bring 
about  the  same  changes  which  will  occur  at  ordinary  tempera- 
tures slowly.  This  is  plausible  and  there  is  something  in  it,  but 
it  is  applicable  only  to  such  coatings  as  are  intended  to  stand  a 
high  heat  because  other  changes  than  oxidation  are  involved. 
It  has  already  been  observed  that  we  know  of  instances  where 
oak  beams  have  been  exposed  to  the  air  for  a  thousand  years 
without  injury,  while  two  hours  in  an  oven  at  400°  Fahr.  will 
begin  the  decomposition  of  wood.  Now  the  ratio  between  two 
hours  and  a  thousand  years  is  as  one  to  over  four  millions,  which 
shows  the  utter  absurdity  of  any  such  test  if  applied  to  miscel- 
laneous coatings.  The  preceding  tables  show  the  same  thing  in 
a  different  way.  Some  of  the  coatings  were  improved  by  baking, 
others  were  injured.  Those  which  were  designed  by  the  makers 
to  be  baked  were  bettered,  and  those  which  were  planned  to  give 
the  best  results  without  baking  were  injured.  To  make  a  suitable 
compound  to  be  applied  by  baking  at  a  high  temperature  which 
will  show  mechanical  toughness,  elasticity,  and  hardness,  com- 
bined with  chemical  inertness  and  permanence  in  the  finished 
product,  is  the  most  difficult  thing  yet  attempted  in  this  kind 
of  work.  In  such  a  compound  the  process  of  baking  effects  a 
chemical  union  among  its  constituents  as  well  as  with  the  atmos- 
pheric oxygen.  In  what  has  been  said  about  the  varnishes  and 


246  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

enamel  paints  employed  in  the  foregoing  tests,  the  subject  of  the 
use  of  these  compounds  for  the  protection  of  steel  is  tolerably  well 
covered.  These  experiments  are,  of  course,  greatly  amplified 
and  supplemented  by  the  experience  of  the  author  in  the  actual 
protection  of  structures  in  great  variety,  leading  to  the  following 
general  conclusions: 

Ordinary  varnishes  are  made  to  combine  two  functions;  one 
is  the  protection  of  the  surface  to  which  they  are  applied,  the 
other  is  to  provide  it  with  a  hard  and  brilliant  coating  which 
serves  for  ornament.  To  secure  the  latter  it  is  necessary  to  have 
the  resin  constitute  about  one-third  to  three-elevenths  of  the 
weight  of  the  dry  film;  these  proportions  correspond  to  varnishes 
made  with  from  20  to  26  gals,  of  oil  to  100  Ibs.  of  unmelted 
resin.  Varnishes  made  for  interior  use  have  sufficient  dura- 
bility even  if  the  proportion  of  resin  exceeds  this,  and  as  the  resin- 
ous ingredient  increases,  so  does  the  brilliancy  of  the  varnished 
surface,  and  polishing-varnishes  seldom  have  more  than  about 
60  Ibs.,  say  8  gals.,  of  oil  to  100  Ibs.  of  resin,  or  the  film  will 
contain  considerably  more  than  half  its  weight  of  resin,  after 
allowing  for  the  loss  of  the  latter  in  melting.  Such  is  the  char- 
acter of  commercial  varnishes;  but  when  we  have  reached  the 
maximum  of  26  gals,  of  oil  we  have  only  begun  to  approach 
the  amount  necessary  for  the  highest  degree  of  durability  with- 
out adornment,  which  is  sought  in  the  protection  of  metal  from 
corrosion. 

Varnish  for  Steel  Structures. — For  this  purpose  a  varnish 
of  26  gals,  of  oil  to  the  100  Ibs.  of  resin  may  perhaps  answer,  but 
we  know  that  30  gals,  is  better  and  for  many  places  a  4o-gal. 
varnish  is  better  than  a  30.  The  broad  statement  may  then  be 
made  that  varnishes  made  for  any  ordinary  use  on  wood  are  not 
suitable,  not  sufficiently  elastic,  for  use  on  structural  steel;  and 
conversely,  that  a  varnish  soft  and  elastic  enough  to  be  right 
for  the  latter  purpose  has  not  enough  hardness  and  lustre  for 
general  use.  It  will,  of  course,  be  much  harder  and  more  lus- 
trous than  an  oil-film,  because  oil  is  the  softening  ingredient 
in  varnish,  and  the  added  resin  imparts  hardness  and  brilliancy 


PROTECTION  OF  METALS  AGAINST  CORROSION.       247 

and  smoothness  of  surface;  and  it  also  acts,  as  has  been 
explained,  as  a  flux,  promoting  in  an  extraordinary  degree  the 
uniform  and  continuous  oxidation  of  the  compound  (or  the  oil 
which  it  contains)  and  thus  producing  a  continuous  and  non- 
porous  film.  A  4o-gal.  varnish  contains  in  the  dry  film  resin  in 
the  proportion  of  i  part  to  4  parts  of  oil;  this  may  seem  to  the 
unpractised  reader,  or  perhaps  even  to  the  experienced  user  of 
hard  varnishes,  not  enough  to  have  much  effect,  but  it  is.  Prob- 
ably almost  every  practising  chemist  has  some  time  tried  to 
dissolve  an  old  gold  pen  in  nitric  acid;  the  base  metal,  chiefly 
copper  and  zinc,  alloyed  with  the  gold  not  only  makes  the  article 
cheaper,  but  -adds  to  its  rigidity  and  elasticity,  and  frequently 
amounts  to  two-thirds  of  the  weight;  and  this  is  easily  soluble  in 
acid,  in  which  the  gold  is  insoluble;  but  every  one  who  has  tried 
it  has  been  astonished  to  see  how  much  the  small  amount  of  gold 
protects  the  large  amount  of  base  metal,  and  how  long  a  time  it 
takes  to  dissolve  out  the  latter.  It  is  exactly  so  with  a  varnish: 
the  effect  of  the  resinous  ingredient  is  out  of  all  proportion  to  the 
amount  present.  It  is  quite  likely  that  this  proportion  of  4  parts 
of  oil  to  i  of  the  melted  resin  is  as  great  as  can  be  made  to  enter 
into  true  combination  and  that  any  further  increase  only  dilutes 
the  varnish  with  oil ;  certainly  the  making  of  a  really  good  varnish 
with  so  much  oil  as  this  is  a  matter  of  difficulty;  in  fact,  as  a 
general  rule,  the  less  oil  there  is  in  a  varnish  the  easier  it  is 
to  make,  and  a  ic-gal.  varnish,  for  example,  diluted  with  10  gals, 
of  oil  is  not  in  the  least  like  a  2o-gal.  varnish.  The  oil  and  resin 
must  be  combined  in  the  making,  and  no  varnish  can  have  a 
high  degree  of  durability  unless  its  ingredients  are  thoroughly 
united.  It  is,  moreover,  desirable,  indeed  indispensable,  for 
reasons  already  explained,  that  it  should  contain  a  minimum 
amount  of  "drier,"  or  lead  and  manganese  compounds.  There 
are  structures  which,  on  account  of  their  location  and  use,  require 
a  varnish  having  more  than  the  minimum  degree  of  hardness 
and  smoothness  in  the  coating.  Where  the  proportion  of  oil 
must  fall  as  low  as  thirty  gallons,  perhaps  sometimes  even  less, 
such  things  are  best  known  by  experience  and  observation.  The 


248  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

making  of  varnishes  for  such  work  is  not  a  job  for  the  inex- 
perienced amateur,  but  for  the  scientific  investigator,  who  may 
well  be,  in  the  best  sense,  an  amateur  varnish-maker,  it  offers  a 
large  and  important  field  for  practical  and  theoretical  research. 

The  most  serious  objection  to  the  use  of  varnish  as  a  protec- 
tive coating  is  the  thinness  of  the  film,  which,  although  greater 
than  that  of  an  oil-film,  is  less  than  that  of  a  good  oil  paint,  and 
is  usually  too  thin  for  permanent  service.  This  may  be  remedied 
by  making  the  varnish  heavier  in  body  or  more  viscous,  and  it 
may  be  thus  made  so  thick  that  any  desired  thickness  of  film  can 
be  obtained.  If  in  making  varnish  the  cooking  be  stopped  as 
soon  as  the  oil  and  resin  have  combined  enough  so  that  they  will 
not  separate  on  cooling,  the  product,  if  it  contains  a  large  pro- 
portion of  oil,  will  be  sufficiently  fluid  for  use  with  a  compara- 
tively small  proportion  of  spirits  of  turpentine;  it  thus  contains  a 
large  percentage  of  non- volatile  ingredients,  which  in  itself  is  of 
advantage;  but  in  such  a  varnish  the  oil  has  not  become  suffi- 
ciently united  with  the  resin,  and  its  durability  will  not  be  as 
great  as  that  of  a  well- cooked  varnish. 

Enamel  Paints. — It  has  already  been  said  that  pigments  can 
be  used  in  varnish  just  as  in  oil,  and  the  varnish  paints,  or  enamels, 
as  they  are  sometimes  called,  are,  if  made  of  proper  materials, 
highly  suitable  for  painting  structural  metal,  especially  bridges. 
Some  of  these  varnish  paints,  which  naturally  exceed  in  thick- 
ness and  hardness  of  film  the  varnishes  themselves,  while  they 
retain  all  their  elasticity,  are  coatings  of  great  beauty  and  per- 
manence. The  cost  of  properly  applying  a  protective  coating  to 
structural  metal  is  often  as  great  as  the  cost  of  the  paint  or  var- 
nish itself  and  not  infrequently  much  more.  There  are  places 
where  it  costs  $3  or  $4  for  labor  to  apply  a  gallon  of  varnish  to  a 
clean  surface,  and  it  is  not  at  all  uncommon  to  spend  $3  in  clean- 
ing the  surface  to  which  a  gallon  is  to  be  applied. 

True  Economy  in  Painting. — Quite  a  good  many  bridges  are 
now  cleaned  either  wholly  or  in  part  with  the  sand-blast,  and  this 
probably  cannot  be  done  at  present  for  less  than  2  cents  per  square 
foot.  A  gallon  of  paint  will  cover  at  least  300  sq.  ft.;  the  cost 


PROTECTION  OF  METALS  AGAINST  CORROSION.       249 

of  sand-blasting  this  would  be  at  least  $6.    A  dollar  would  proba- 
bly be  the  minimum  cost  of  labor  to  apply  a  gallon  of  paint  in  such 
a  place;   this  makes  $7*.    Suppose  that  a  gallon  of  good  oil  paint 
can  be  had  for  a  dollar;   the  total  cost  is  $8.     Now  suppose  that 
a  varnish  enamel  paint  for  the  purpose  can  be  had  for  $3  a  gallon; 
the  cost  of  a  gallon  of  such  paint  would  be  when  applied  $10. 
Obviously,  if  it  lasts  25  per  cent,  longer  than  the  oil  paint  it  is 
as  cheap,  and  it  certainly  looks  better.     If,  however,  it  costs  only 
$2  to  clean  the  metal,  the  prices  will  become  $4  and  $6,  and  the 
enamel  must  last  50  per  cent,  longer,  and  so  on.    The  results  of 
the  tests  which  have  been  given  in  detail, — and  it  may  be  here 
said  that  all  the  plates  of  the  1897-99  tests  were  exhibited  before 
the  American  Society  of  Civil  Engineers,  in  New  York,  the  Bos^ 
ton  Society  of  Civil  Engineers,  and  the  Engineers'  Club,  of  Phil- 
adelphia,— certainly  indicate  that  the  best  varnishes  and  varnish 
enamels  exceeded  the  best  oil  paints,  and  even  red  lead,  more  than 
100  per  cent.,  and  probably  very  much  more  than  that;   and  I 
believe  this  is  fully  borne  out  in  .practice,  and  that  where  perma- 
nent protection  is  wanted  and  repainting  from  time  to  time  is 
anticipated,  a  good  enamel  paint,  by  preference  one  not  contain- 
ing much  white  pigment,  is  an  economical  paint  to  use.    I  am 
also  satisfied  that  a  good  durable  black  varnish  without  pigment, 
containing  a  reasonable  amount  of  asphaltum  and  a  large  pro- 
portion of  oil,  can  be  made  for  such  purposes  at  a  very  moderate 
price  and  will  outlast  any  oil  or  red-lead  paint.    Asphaltum,  if 
so  combined  as  to  prevent  its  crumbling,  is  very  efficient  in  retard- 
ing oxidation,  and  is  a  most  valuable  ingredient  in  a  varnish  where 
its  color  is  not  an  objection.     It  has  so  far  been  quite  impossible 
for  any  one  to  produce  a  baking  enamel  without  asphaltum  which 
can  at  all  compare  in  durability  and  indifference  to  chemical 
action  with  the  best  of  the  enamels  in  which  it  is  an  ingredient. 

Covering  Capacity  of  Paint. — In  painting  structural  steel  or 
iron  it  is  a  general  rule  that  any  good  paint  or  varnish  covers 
-about  300  to  400  sq.  ft.  to  the  gallon,  one  coat.  Almost  any  paint 
may  be  brushed  out  thin  enough  to  cover  from  50  to  100  per  cent, 
more  surface  than  this,  but  this  is  not  profitable,  for  the  labor 


250  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

costs  more  than  the  paint,  and  the  object  of  the  painter  should 
always  be  to  apply  as  heavy  a  coat  as  will  dry  uniformly.  On 
rough  surfaces  more  paint  is  used  than  on  smooth  and  less  is  used 
on  the  second  coat  than  the  first.  Tables  have  been  published 
showing  much  greater  covering  capacity  than  400  sq.  ft.,  and  no 
doubt  450  is  a  practicable  number  on  flat,  smooth  work,  such  as 
roofs  and  the  like,  and  I  have  been  shown  evidence  by  railway 
companies  that  red  lead  may  be  depended  on  to  cover  at  least 
600,  but  I  have  observed  that  some  of  these  people  who  find  such 
high  covering  capacity  are  always  finding  fault  with  the  dura- 
bility of  the  paint,  which  is  probably  evidence  that  they  are  hav- 
ing it  brushed  out  too  thin,  and  some  of  them  follow  the  practice 
already  commended,  of  having  a  regular  painter's  crew  retouching 
all  doubtful  spots  continually,  so  that  they  are  unable  to  judge  of 
the  economy  of  thin  painting.  Besides  this,  it  is  not  to  be  for- 
gotten that  the  surface  painted  is  rarely  measured,  but  is  usually 
guessed,  and  a  guess  usually  allows  for  more  work  than  has  been 
done.  Very  opaque  pigments,  such  as  are  commonly  used  in 
structural  work,  iron  oxides,  graphites,  carbon  pigments,  and  red 
lead,  lend  themselves  to  this  practice  of  thin  painting,  but  this, 
though  a  merit  in  a  decorative  paint,  is  the  opposite  in  a  struc- 
tural one,  where  thickness  of  film  is  one  of  the  prime  requisites. 
Anything  which  makes  it  more  troublesome  to  get  good  work 
done  is  objectionable,  for  it  is  natural  to  neglect  doing  that  which 
can  be  avoided,  and  even  with  the  best  intentions  men  forget; 
they  always  have,  and  they  always  will;  the  intention  is  lost 
sight  of  in  the  routine  of  daily  toil.  On  this  ground  the  use  of 
the  less  opaque  varnishes  and  varnish  paints  is  preferable;  the 
workmen  can  see  as  they  work  if  they  are  putting  on  too  thin  a 
coat. 

The  selling  price  of  a  paint  or  other  protective  coating  often 
determines  the  question  of  its  use  or  the  reverse.  Economy  is 
always  desirable,  but  it  is  not  always  gained  by  the  purchase  of 
inexpensive  material.  Cost  should  be  considered  in  the  pur- 
chase of  supplies,  but  it  is  important  that  when  paid  for  they 
should  be  suited  to  their  use.  For  example,  if  a  contractor  has 


PROTECTION  OF  METALS  AGAINST  CORROSION.       251 

metal  used  for  scaffolding  and  other  false  work  which  will  be 
frequently  removed  and  erected  and  from  which  the  paint  will 
be  mechanically  removed,  so  that  it  has  to  be  repainted  at  fre- 
quent intervals,  a  cheap  paint  is  as  good  as  any;  the  same  is 
true  of  all  temporary  structures;  money  may  be  saved  in  many 
instances  by  buying  cheap  paint.  But  if  the  exposure  is  severe, 
or  if  the  structure  is  to  receive  little  attention,  it  will  be  econom- 
ical to  buy  a  good  paint.  Bridges  painted  with  good  oil  paints 
require,  unless  very  favorably  situated,  repainting  every  three  to 
five  years;  less  often  in  a  cold,  arid  country.  If  a  better  paint 
will  last  ten  years  instead  of  five,  we  must  consider  that  the  cost 
of  the  cheaper  paint,  which  for  convenience  we  will  say  is  $i  a 
gallon,  amounts  to  $2.75  in  ten  years,  reckoning  two  paintings 
and  compound  interest  at  5  per  cent.  The  equivalent  of  this 
would  be  an  enamel  paint  at  a  first  cost  of  $1.86  per  gallon  to 
last  ten  years. 

Cost  of  Application. — But  we  must  not  omit  the  cost  of  clean- 
ing and  repainting  at  the  end  of  the  first  five  years  with  the  cheaper 
paint,  which  could  not  be  less  than  $i  per  gallon,  and  this  addition 
would  make  it  proper  to  pay  $2.71  per  gallon  for  a  ten-year  paint, 
as  against  $i  a  gallon  for  a  five-year  paint.  The  above  figures 
are  assumed,  merely  to  show  the  principle  involved;  in  reality 
the  cost  of  oil  paints  will  vary  with  the  cost  of  materials  from 
75  cents  to  $1.50,  and  of  varnishes  and  varnish  paints  from 
$1.50  to  $3,  or  more,  and,  as  has  been  already  stated,  the  cost  of 
cleaning  and  repainting  may  run  up  to  $6  or  $8  per  gallon  of 
paint  used. 

Cost  of  Paint. — Even  the  cheapest  oil  paints,  those  made  of 
iron  oxides  and  graphites,  cost  something,  more  than  most  people 
imagine.  Linseed-oil  varies  in  price  from  about  40  to  80  cents 
per  gallon,  and  some  time  ago  when  oil  was  at  56  cents,  a  fair 
medium  price,  the  writer  went  over  this  matter  with  the  superin- 
tendent of  one  of  the  largest  and  best  paint-factories  in  the  coun- 
try, trying  to  get  at  the  absolute  minimum  cost  of  such  a  paint. 
In  the  first  place,  a  gallon  of  paint  contains  about  6J  Ibs.  of  oxide, 
worth,  say,  pj  cents,  and  6J  Ibs.  of  oil,  which  at  56  cents  per 


252  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

gallon,  is  worth  about  46 J  cents,  making  56  cents  for  material. 
Now,  if  it  is  mixed  in  a  paint-mixer,  not  ground  through  a  mill, 
as  it  ought  to  be,  but  as  it  is  not  usually,  and  is  made  in  large 
quantities,  the  cost  of  labor  and  power  may  be  figured  down  to,, 
perhaps,  ij  cents  per  gallon,  without  allowing  anything  for  super- 
vision; \  cent  per  gallon  must  be  added  for  wear  and  tear;  it 
costs  at  least  2  cents  per  gallon  for  barrels,  and  i  J  cents  to  deliver 
it  f.o.b.  in  New  York,  making  in  all  5  cents  per  gallon.  If  to 
this  is  made  an  allowance  for  superintendence,  rent,  insurance, 
and  interest  on  capital  invested,  at  least  5  cents  more  must  be 
added,  making  the  actual  cost  under  the  most  favorable  cir- 
cumstances 66  cents  per  gallon.  If  it  is  to  be  put  through  a 
mill,  the  cost  of  labor  and  power  will  be  not  less  than  2  cents 
per  gallon  additional,  with  another  addition  for  superintendence, 
etc.,  which  would  bring  the  cost  up  to  70  cents.  But  in  any 
manufacturing  business  there  is  more  or  less  loss  of  material 
and  of  time,  and  there  must  be  also  some  little  profit;  and  it 
was  the  opinion  of  the  expert  that  any  man  who  attempted  ta 
sell  a  perfectly  straight  well-made  oxide  at  75  cents  per  gallon 
would  lose  money.  In  the  factory  where  he  is  superintendent, 
it  is  necessary  to  grind  certain  cheap  paints  and  deliver  them,, 
without  packages,  to  another  department  of  the  same  factory; 
and  it  is  customary  to  charge  the  second  department  i  cent  per 
pound  for  grinding,  which,  in  this  case,  would  be  12^  cents  per 
gallon,  which  is  the  estimated  actual  cost;  this  substantially 
agrees  with  the  figures  given.  A  large  manufacturer  in  Canada, 
where  labor  is  cheaper  than  here,  contracted  to  have  his  liquid 
paints  ground  and  put  into  the  packages  which  he  furnished 
for  2  cents  per  pound  for  labor  only,  which  would  be  25  cents 
per  gallon  on  oxide  paints;  this  was  cheaper  than  he  could  do 
it  himself  and  proved  to  be  too  little  to  remunerate  the  con- 
tractor. 

The  cost  of  a  gallon  of  pure  red-lead  paint,  very  hastily  and 
imperfectly  mixed  (as  it  must  be)  just  before  using,  cannot  be 
less  than  $1.50  per  gallon,  and  probably  is  a  good  deal  more 
than  that.  The  exact  cost  cannot  be  computed  without  know- 


PROTECTION   OF  METALS  AGAINST  CORROSION,       253 

ing  the  amount  of  pigment  used,  in  regard  to  which  practice  is 
variable;  but  20  Ibs.  per  gallon  makes  a  very  thin  paint.  The 
cost  may  run  up  to  $2  per  gallon.  This  question  of  cost  of  paint 
is  of  more  importance  than  it  might  seem  at  first  sight,  for  it 
is  evident  that  a  very  cheap  paint  is  not  what  it  is  pretended 
to  be,  and,  if  so,  doubt  is  at  once  thrown  on  its  whole  value. 
As  a  general  rule,  no  really  first-class  goods  can  be  made  without 
skilled  labor,  and  the  more  skilled  labor  used,  the  greater  will 
be  the  cost.  A  thing  is  not  good  merely  because  it  is  expensive; 
but  if  it  is  a  thing  which  is  capable  of  being  made  better  by  skill, 
then  the  best  of  the  sort  cannot  be  cheap,  and  is  yet  likely  to  be 
most  economical  in  use.  When  paint  is  offered  at  less  than  75 
cents  a  gallon  the  price  is  against  it,  and  it  is  easy  to  make  a  plain 
oil  and  pigment  paint  which  is  honestly  worth,  from  the  factory 
standpoint,  $1.50  per  gallon. 

Spraying-machines. — Paint  is  usually  applied  with  a  brush, 
but  within  the  last  ten  years  a  great  deal  of  it  has  been  put  on 
with  spraying- machines,  which  operate  with  compressed  air 
and  spray  the  paint  over  the  surface.  These  work  well  on  large 
flat  surfaces,  but  if  used  on  bridge  work  or  anything  of  that  kind, 
there  is  a  considerable  waste  of  paint  caused  by  the  narrowness 
of  the  pieces  to  be  painted;  part  of  the  paint  floats  off  in  the  air 
and  is  lost,  and  unless  the  paint  is  very  cheap  the  loss  of  paint 
makes  up  for  the  economy  of  labor,  so  that  as  a  matter  of  fact 
these  machines  are  very  little  used  on  structural  work.  Their 
principal  use  is  in  painting  freight -cars;  almost  any  one  can  hit 
the  side  of  a  car  if  he  stands  near  enough  and  a  couple  of  men 
can  paint  a  car  in  three  or  four  minutes. 

There  is  difference  of  opinion  as  to  the  comparative  merits 
of  machine  and  brush  work.  The  advantage  of  the  machine  is  that 
the  spray  is  carried  along  in  a  current  of  air  and  so  penetrates 
cracks  and  recesses  which  are  inaccessible  to  the  brush  and  it  does 
not  skip  anything;  the  most  irregular  surface  is  as  well  painted 
as  a  plain  one.  The  advantage  of  the  brush  is  that  the  paint 
may  be  rubbed  with  more  force  into  the  surface,  and  the  universal 
belief  is  that  a  paint  well  rubbed  out  is  more  durable  than  one 


254  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

less  carefully  applied.  There  is  much  difference  in  the  quality 
of  work  done  with  the  brush.  In  the  first  place,  there  are  differ- 
ences in  brushes.  A  cheap  or  worn-out  brush  containing  not 
enough  bristlc-s  does  not  absorb  enough  paint.  In  order  to  put 
on  a  full,  flowing  coat  the  brush  should  be  capable  of  holding 
enough  paint  to  act  as  a  sort  of  reservoir,  so  that  the  end  of  the 
brush  which  comes  in  actual  contact  with  the  surface  will  be 
for  a  reasonable  time  amply  supplied  with  paint  and  will  not 
•drag  and  pull  on  the  surface.  With  a  dense,  well-made  brush, 
.saturated  with  paint,  the  workman  can  spread  and  rub  out  the 
paint  without  having  it  absorbed  again  by  the  brush. 

Sometimes  a  skilful  house-painter  makes  ,a  poor  job  on 
structural  steel  work  for  the  reason  that  he  has  been  accustomed 
to  rub  out  his  paint  very  thin,  so  as  to  make  an  excessively  thin, 
smooth  coat,  and  one  which  will  dry  quickly;  whereas,  the  pri- 
mary thing  in  this  work  is  to  put  on  a  full,  heavy  coat,  which  will 
afford  protection  to  the  metal,  and  while  it  is  better  to  be  smooth, 
it  is  necessary  that  it  should  not  be  thin.  House-painters,  more- 
over, find  it  hard  to  believe  that  a  slow-drying  elastic  paint  is 
fit  for  any  use  and  are  possessed  with  a  determination  to  improve 
it  by  the  addition  of  driers.  In  such  a  state  of  affairs  about  two 
inspectors  are  needed  to  watch  each  painter. 

Influence  of  the  Weather. — It  is  generally  agreed  that  paint 
should  not  be  applied  in  wet  or  freezing  weather,  but  one  side 
of  a  bridge  is  frequently  shaded,  and  its  temperature  may  be 
less  than  that  of  the  air,  and  if  the  latter  is  saturated  with  moist- 
ure, or  nearly  so,  the  sunny  side  of  the  bridge  may  be  dry  and 
in  good  condition  to  paint  and  the  shaded  side  covered  with 
<lew.  Similarly,  bridges  often  span  cool,  dark  ravines,  and  some- 
times there  are  only  a  few  hours  in  the  middle  of  the  day  when 
such  a  bridge  is  in  the  best  condition  to  paint.  So  it  appears  that 
besides  proper  cleaning  of  the  structure  and  selection  of  the  most 
.suitable  paint  it  is  important  and  sometimes  difficult  to  get  the 
paint  put  on  in  the  best  manner.  Unless  the  metal  in  a  structure 
can  be  enclosed  so  as  to  keep  the  air  away  from  it,  it  is  probably 
desirable  to  expose  it  to  a  free  circulation,  with  the  aim  of  keep- 


PROTECTION  OF  METALS  AGAINST  CORROSION.       255 

ing  it  all  as  nearly  as  may  be  at  the  same  temperature,  so  that  no 
part  of  it  shall  be  so  shaded  or  protected  as  to  have  its  temperature 
below  the  dew-point. 

It  should  not  be  forgotten  that  strength,  though  essential,  is 
not  the  only  desirable  quality  for  a  bridge.  Rigidity  is  very 
important  and  greatly  promotes  the  preservation  of  the  metal, 
for  if  the  bridge  vibrates  when  a  load  passes  over  it,  as  many 
highway  bridges  and  some  railway  bridges  do,  the  joints  become 
loosened,  and  if  wet  with  rain  or  snow  the  water  is  mechanically 
worked  into  the  joints,  the  paint  which  was  put  there  is  broken 
up  and  destroyed,  and  rusting  is  promoted  in  a  decided  manner. 

Some  engineers  object  to  specifying  the  use  of  a  particular 
paint  or  other  similar  coating,  the  product  of  a  single  maker, 
believing  that  this  prevents  competition  in  bids  and  results  in 
the. payment  of  a  higher  price  than  would  otherwise  be  necessary. 
They  also  seem  apprehensive  that  such  a  course  may  injure  their 
reputation  by  the  suggestion  that  they  receive  a  commission  from 
the  manufacturer.  As  to  this  latter  point,  the  writer  does  not 
believe  there  are  many  engineers  whose  characters  are  not  good 
enough  to  clear  them  from  any  such  suspicion,  and  those  who 
cannot  be  indifferent  to  such  a  matter  probably  have  not  a  great 
deal  of  reputation  to  be  damaged.  An  engineer  or  architect 
should  regard  his  employers'  or  clients'  interests  as  though  they 
were  his  own,  and  if  he  thinks  the  best  results  are  likely  to  be 
obtained  by  using  a  particular  paint  or  varnish,  he  ought  to  call 
for  it  in  his  specifications;  and  the  man  who  acts  on  that  prin- 
ciple can  safely  leave  his  reputation  to  take  care  of  itself. 

It  is  perfectly  easy  to  get  a  competitive  price.  Let  the  engi- 
neer, before  writing  his  specification,  ask  the  price  from  the 
manufacturer;  he  can  thus  protect  the  contractor,  for  while  the 
manufacturer  cannot  guarantee  the  durability  of  his  material, 
which  depends  in  great  part  on  the  preparation  of  the  surface 
and  the  care  taken  in  applying  the  coating,  he  can  always  tell  the 
price.  That  is  the  only  thing  he  can  properly  guarantee.  There 
are  too  many  engineers,  and  some  of  them  holding  high  positions, 
who  seem  to  think  they  are  not  doing  their  duty  to  their  employers 


256  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

unless  everybody  they  do  business  with  loses  money.  No  more 
ruinous  idea  than  this  can  be  held.  No  business  man  wants  to 
do  business  with  any  one  who  is  not  making  a  profit  and  who 
consequently  has  an  incentive  to  give  satisfaction. 

Business  Principles. — Too  many  professional  men  are  unedu- 
cated in  business  and  are  ignorant  of  the  principles  by  which  it 
is  conducted,  the  most  fundamental  of  which  is  that  in  any 
legitimate  business  transaction  both  parties  are  benefited.  Any 
man  who  systematically  attempts  to  buy  supplies  for  less  than 
they  are  worth  is  thereby  thrown  into  the  hands  of  sharpers  and 
cheats,  who  try  to  satisfy  him  while  giving  him  inferior  material. 
Perhaps  it  is  not  right  to  call  them  cheats,  for  our  courts  have 
decided  that  a  man  who  contracted  for  and  paid  for  a  turpentine 
japan  at  less  than  the  price  of  turpentine  was  not  defrauded 
when  he  received  a  benzine  japan  and  could  not  recover  pay- 
ment, for  it  is  assumed  that  he  could  not  legally  expect  to  buy  a 
thing  for  less  than  it  cost.  This  was  a  famous  and  well-known 
case;  and  the  guilty  man  is  the  one  who,  in  the  first  instance, 
tries  to  perpetrate  the  fraud.  The  employers  of  such  men  deserve 
whatever  they  get. 

The  engineer  must  make  up  his  mind  in  some  way  that  it 
seems  wise  to  use,  on  a  particular  structure,  some  special  paint; 
then  he  ought  to  specify  that  clearly,  with  the  name  and  address 
of  the  maker  if  possible,  and  let  the  contractor  know  at  once 
exactly  what  will  be  required.  This  tends  to  remove  from  the 
latter  a  temptation  to  supply  an  inferior  article  and  makes  it  far 
easier  to  have  proper  inspection.  If,  in  addition,  the  manufacturer 
is  notified  and  told  who  will  buy  the  materials  and  the  quantity 
required,  the  chances  are  ten  to  one  that  he  will  make  a  special 
test  to  see  that  they  are  not  for  any  reason  below  the  standard. 
The  maker  takes  far  more  interest  in  such  an  order  than  he  does 
in  goods  for  miscellaneous  trade,  to  be  used  he  knows  not  by 
whom,  or  how,  or  where.  Fair  and  straightforward  treatment 
will  always  secure  the  interest  and  cordial  co-operation  of  the 
manufacturer.  It  is  not  straightforward  to  say  that  the  paint 
used  shall  be  either  of  those  made  by  Jones,  by  Brown,  or  by 


PROTECTION  OF  METALS  AGAINST  CORROSION.       257 

Robinson,  when  everybody  knows  that  Jones  sells  his  paint  at  $i 
a  gallon,  Brown  at  $1.25,  and  Robinson  at  $1.50.  This  is  merely 
an  attempt  on  the  part  of  an  engineer  to  "save  his  face,"  as  the 
Chinese  say;  it  deceives  no  one;  it  is  undignified;  it  gains  the 
respect  of  none  and  forfeits  that  of  many.  On  public  works  the 
law  sometimes  requires  such  subterfuges,  and  then  they  may  be 
excusable;  but  the  actual  result  of  such  restrictions  is  that  in 
the  purchase  of  that  class  of  supplies  for  which  accurate  descrip- 
tive specifications  cannot  be  written,  some  execrable  materials 
which  would  not  be  considered  for  a  moment  by  any  intelligent 
private  citizen  have  to  be  accepted.  There  is  no  part  of  our 
public  service  which  stands  in  greater  need  of  reform  than  this 
matter  of  purchasing  supplies. 


CHAPTER   XVI. 
WATER-PIPE   COATING. 

THE  engineers  of  water-supply  are  constantly  in  trouble  on 
account  of  the  corrosion  of  the  metal  pipes  used  in  conveying 
water.  Nearly  all  of  these  pipes  are  iron  and  almost  all  the 
large  pipes  tare  of  cast  iron.  This  metal  does  not  rust  as  readily 
as  wrought  iron  or  steel,  and  it  is  necessary  to  make  it  much 
thicker  than  steel  because  of  its  inferior  strength  and  greater 
brittleness  and  also  because  it  is  liable  to  have  thin  or  defective 
spots,  which  is  not  the  case  with  steel  or  iron  pipe.  It  does  not 
therefore  rust  through,  as  a  rule,  as  easily  as  the  others.  On  the 
other  hand,  it  is  not  as  tight,  it  is  liable  to  leak  at  the  joints,  and 
to  be  broken  by  the  unequal  settling  of  the  earth  about  it,  and 
on  account  of  its  greater  weight  it  costs  more,  at  least  in  large 
sizes,  say  above  4  feet  in  diameter. 

Rusting  of  Cast  Iron. — Rust  is,  however,  a  very  serious  cause 
of  trouble  with  cast-iron  pipe;  it  causes  the  surface  to  become 
rough,  and  this  interferes  with  the  free  flow  of  water.  Cast  iron 
is  not  a  homogeneous  material,  and  rusting  begins  at  spots  where 
the  chemical  action  is  most  strongly  induced,  which  may  be  due 
to  galvanic  action  due  to  the  proximity  of  portions  of  different 
composition,  or  often  to  the  leakage  to  the  pipe  of  an  electric 
current  from  an  outside  source.  The  spot  becomes  covered  with 
a  mass  of  hydrated  sesquioxide  of  iron,  very  bulky  in  proportion 
to  its  weight  (and  its  weight  is  two-thirds  greater  than  that  of  the 
iron  which  it  contains),  and  this  coating  is  believed  to  act  cata- 
lytically  to  induce  further  corrosion;  at  any  rate,  the  spot  soon 
becomes  covered  with  a  nodule  of  rust,  projecting  an  inch  or  two, 

and  sometimes  much  more,  into  the  interior  space;   this  not  only 

258 


WATER-PIPE  COATING.  259 

diminishes  the  cross-section  of  the  opening,  but,  what  is  still 
more  important,  sets  up  irregular  and  vortex  currents  which  very 
seriously  affect  the  free  €ow  of  water  through  the  pipe. 

Diminished  Flow. — The  rough  surface  thus  produced  also 
serves  for  a  foothold  for  algae  and  other  vegetable  growths,  which 
attach  themselves  to  the  wall  of  the  pipe  and  float  in  the  current 
of  water,  from  which  they  derive  their  sustenance,  and  to  which 
in  some  instances  they  impart  taste  and  odor,  the  combined 
result  being  that  often  the  flow  of  water  through  a  long  water- 
main  is  diminished  25  per  cent.,  and  sometimes  50  per  cent,  or 
more.  It  is,  therefore,  desirable  for  more  reasons  than  one  to 
prevent  corrosion,  even  in  cast-iron  pipes;  as  for  steel  pipes, 
these  are  so  thin  that  comparatively  little  corrosion  causes  a  leak,, 
sometimes  amounting  to  a  serious  failure  of  the  pipe,  and  must 
be  prevented  at  any  cost. 

The  R.  Angus  Smith  Patent. — What  may  be  regarded  as  the 
beginning  of  the  modern  practice  of  pipe- coating  was  the  inven- 
tion of  Robert  Angus  Smith,  Ph.D.,  F.C.S.,  a  citizen  of  Man- 
chester, England,  and  for  a  long  time  Secretary  of  the  Literary 
and  Philosophical  Society  of  Manchester.  He  was  the  author  of 
many  scientific  papers,  and  at  the  request  of  the  society  prepared 
a  Memoir  of  John  Dalton,  the  eminent  chemist,  who  was  also  a 
member  of  that  soceity.  Dr.  Smith  (who  was  not  a  medical  man, 
but  a  scientific  chemist  and  a  physicist)  was  applied  to  for  advice 
in  the  matter  of  protecting  the  water-pipes  laid  down  by  the  city 
of  Manchester  between  1845  and  1850,  probably  because  he  was 
the  secretary  and  permanent  executive  officer  of  the  society 
before  mentioned,  which  included  many  eminent  technical  and 
scientific  men  of  Manchester  and  neighboring  cities.  The  result 
of  his  investigations  and  experiments  is  set  forth  in  the  patent  for 
coating  pipes  which  was  issued  to  him  October  19,  1848,  and  is 
No.  12,291  of  the  British  Patent  Office.  In  the  specifications 
he  says  that  "the  coal-tar"  (which  was  the  principal  ingredient, 
in  his  estimation,  of  his  coating)  "is  first  to  be  reduced  by  dis- 
tillation or  otherwise,  so  as  to  obtain  the  product,  which  consists 
of  a  thick  pitch-like  mass;  this  is  to  be  kept  at  a  temperature  of 


260  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

300°  F.  (or  such  a  temperature  as  will  keep  the  matter  fluid). 
The  pipes  to  be  coated  are  first  to  have  their  interior  surfaces 
cleansed  from  oxide,  so  as  to  offer  a  clean  metal  surface,  which  I 
prefer  to  coat  over  with  linseed-oil.  They  are  then  to  be  heated 
to  300°  F.  in  a  suitable  stove,  then  immersed  in  the  melted 
coal-tar  and  remain  there  an  hour."  He  also  recommends  the 
addition  of  linseed-oil  to  the  coal-tar  to  keep  it  of  the  proper  con- 
sistency; and  although  it  is  known  that  he  also  made  various  com- 
pounds of  coal-tar  containing  Burgundy  pitch  and  other  resinous 
and  oily  substances,  in  this  respect  exactly  agreeing  with  the  prac- 
tice of  the  varnish-makers  of  the  time,  it  is  clear  that  his  primary 
and  essential  compound  was  composed  of  coal-tar  distilled  until 
it  became  a  sort  of  artificial  asphalt,  which  would  not  easily  be 
further  changed  by  the  action  of  air  or  water  because  it  had  lost 
all  its  easily  volatile  constituents;  this  coal-tar  pitch,  the  residue 
of  distillation  at  300°  F.  or  over,  was  brittle,  and  to  make  it 
tough  and  elastic  it  was  softened  with  linseed-oil;  and  this  com- 
pound of  linseed-oil  and  coal-tar  pitch  was  used  either  alone  or 
compounded  with  other  oleo-resinous  ingredients.  The  coal-tar 
pitch  was  cheap,  and  its  cheapness  made  it  practicable  to  get 
such  a  compound  applied  to  low-priced  material;  and  this,  I 
presume,  was  the  occasion  for  his  saying  in  his  claim,  "What  I 
claim  is  the  coating  of  the  interior  of  water-pipes  by  coal-tar  by 
the  aid  of  heat."  As  a  result  (probably  an  unforeseen  result) 
of  this  wording  of  the  claim  it  is  legitimate  for  all  users  of  a  coal- 
tar  coating  to  call  it  the  "Angus  Smith  Process,"  although  we 
cannot  doubt  that  he  would  have  unhesitatingly  condemned  the 
current  modern  practice,  both  as  to  materials  and  mode  of  appli- 
cation. 

"The  evil  that  men  do  lives  after  them; 
The  good  is  oft  interred  with  their  bones." 

Let  us  note  particularly  some  of  the  details  of  his  process.  In 
the  first  place,  he  distilled  the  coal-tar  until  he  got  a  pitch-like 
residuum,  which  required  a  temperature  of  300°  F.  or  over  to 
keep  it  fluid.  This  is  the  hard  pitch  prepared  for  roofing-pitch 


WATER-PIPE  COATING.  261 

before  the  latter  has  been  tempered  with  softening  ingredients; 
it  is  hard  enough  to  be  brittle  when  cold. 

Pitch  and  Linseed-oil. — This  hard  pitch  can  be  compounded 
with  linseed-oil,  which  will  not  unite  with  liquid  coal-tar;  on  this 
point  see  the  experiments  of  T.  H.  Wiggin  in  the  Journal  of  the 
Association  of  Engineering  Societies  (Boston),  vol.  22. 

A  Clean  Metal  Surface. — This  compound  of  hard  pitch  and 
linseed-oil  was  applied,  not  to  an  uncleaned  pipe,  but  to  a  pipe 
prepared  by  having  "the  interior  surface  cleaned"  (not  merely 
from  dirt  and  sand,  but)  "from  oxide  so  as  to  offer  a  clean  metal 
surface";  there  is  no  ambiguity  about  that.  Dr.  Smith  was  a 
man  distinguished  for  his  literary  and  scientific  attainments,  and 
knew  exactly  what  his  words  meant. 

Linseed-oil  Coat. — The  inside  of  that  pipe  was  pickled  with 
acid,  and  the  "clean  metal  surface"  was  then  coated  with  linseed- 
oil,  put  in  "a  suitable  stove,"  and  baked  at  300°  F.  Then  it 
was  ready  for  the  pitch  and  linseed-oil  compound,  in  which  it 
was.  immersed  for  "an  hour"  at  300°  F.;  then  it  was  taken  out 
and  the  residual  heat  in  the  mass  of  the  metal  pipe  baked  it 
on  in  a  thin  film.  Note  especially  that  the  first  coat  of  linseed- 
oil  was  baked  on,  and  that  in  this  perfectly  oxidized  and  hardened 
condition  it  could  not  dissolve  in  the  secondary  coating,  even  when 
immersed  in  it  an  hour.  In  another  part  of  the  patent  specifica- 
tion he  advises  that  the  hot  pipe,  when  it  has  been  removed  from 
the  oil-  and  pitch-bath  and  partially  drained,  should  be  slushed 
with  linseed-oil,  to  help  remove  the  excess  of  compound,  and  says 
that  part  of  this  last  application  of  oil  will  run  back  into  the  tank 
and  help  to  keep  it  properly  tempered. 

There  is  no  doubt  that  pipe  treated  in  this  way  will  stand 
service ;  we  can  improve  on  the  details,  with  our  greater  knowledge 
and  resources  of  materials,  but  we  have  not  done  it  with  cast-iron 
pipe,  nor  has  any  such  pipe  been  as  well  coated  since  his  time. 

Present  Method. — The  current  practice  is  thus  described  by 
Mr.  Wiggin,  and  as  the  pipe  was  made  for  the  Metropolitan 
Water  Supply  of  Boston  and  vicinity,  it  was  probably  as  good 
as  could  be  had  in  the  country: 


262  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

"The  inspector  having  passed  judgment  on  the  pipes,  they 
are  rolled  along  down  to  the  coating  apparatus.  The  apparatus 
consists  of  a  number  of  ovens,  with  iron  cars,  on  which  the  pipes 
are  rolled  into  the  ovens  and  on  which  they  stand  during  heating, 
a  vat  or  tank  for  the  coating  compound,  a  crane  for  hoisting 
the  pipes  in  and  out  of  the  vat,  and  various  brushes,  scrapers, 
and  mops  for  brushing  out  dirt  and  removing  surplus  coating 
material.  The  coating  material  is  crude  gas-tar  with  sometimes 
some  dead  oil  of  tar  added.  The  pipes  are  given  a  fairly  good 
brushing  before  being  put  in  the  oven.  The  oven  is  merely  an 
enlarged  chimney-flue,  for  all  the  smoke  and  gases  of  combustion 
pass  in  at  one  end  and  out  at  another,  so  that  a  light  but  visible 
deposit  of  soot  is  made  on  the  pipes,  which  is  not  brushed  off. 
The  old-fashioned  ovens  have  simply  a  square  hole  through  the 
floor  of  the  oven,  connecting  it  with  the  fire,  so  that  the  hot  gases, 
and  occasionally  flame,  act  principally  upon  one  portion  of  the 
pipe,  heating  that  portion  very  hot  before  materially  affecting 
the  other  portions.  The  newer  ovens  are  fitted  with  an  arched 
bottom,  with  bricks  left  out  at  intervals  all  along  the  pipe,  this 
arrangement  causing  a  more  uniform  temperature.  The  pipe 
is  left  in  the  oven  until  the  attendants  think  (no  thermometer  is 
used)  it  is  heated  to  about  the  correct  temperature  (48- in.  pipes 
are  left  in  about  twenty  minutes);  then  it  is  put  in  the  tar  to 
stay  from  a  moment  to  ten  minutes,  according  to  the  condition 
of  the  work  about  the  vat.  On  being  removed  from  the  vat, 
the  pipe  is  allowed  to  drain  over  the  vat,  and  the  drainage  is 
aided  by  scraping  the  invert  with  a  segmental  hoe,  made  to  fit, 
or  at  least  to  be  of  smaller  radius  than  the  pipe.  The  pipe  is 
then  lifted  out  onto  the  skids  and  the  coating  smoothed  up  fur- 
ther— surplus  tar  removed  and  thin  places  reinforced — by  a 
brush  or  mop.  The  brush  is  better  because  the  mop  leaves 
part  of  itself  behind  on  the  pipe.  The  coating  becomes  hard 
in  from  half  an  hour  to  two  hours,  according  to  conditions. 

Kind  of  Tar  Used. — "  Coal-tar  varies  very  widely  according 
to  the  coal  used  and  the  temperature  maintained  in  the  manu- 
facture of  the  gas.  Furthermore,  coal-tar  varies  at  the  different 


WATER-PIPE  COATING.  263 

heights  in  the  tank  in  which  it  is  collected  at  the  gas-works.  But 
no  tests  are  made  to  obtain  any  particular  kind  of  tar  for  coatings. 
The  unrefined  overflow  from  the  hydraulic  main  of  the  gas- 
plants  is  purchased  where  it  can  be  obtained  easiest  and  cheapest. 
Specifications  often  call  for  deodorized  tar,  but  the  most  notice- 
able thing  about  coating-tar  is  its  dense  and  pungent  fumes 
when  heated. 

"In  summer  tar  is  usually  more  fluid  than  molasses;  in 
winter  it  has  often  to  be  melted  out  of  the  barrels.  This 
crude  tar  cannot  be  used  as  a  paint  for  cold  surfaces,  because 
it  will  not  harden;  and  tar  from  the  coating- vat,  though  always 
somewhat  refined  by  the  continued  heating,  does  not  harden 
sufficiently  when  applied  to  cold  surfaces.  This  suggests  the 
philosophy  of  the  whole  tar  process  of  coating.  By  the  heat 
of  the  pipes  the  tar  is  distilled  down  to  a  compound  which  is 
solid  at  atmospheric  temperatures.  A  very  favorable  condition 
for  this  volatilization  of  the  liquefying  constituents  (which  are 
also  the  most  volatile  constituents)  evidently  exists  when  the 
tar  is  exposed  to  the  air,  spread,  as  it  is  then,  in  a  thin  film  over 
the  hot  pipes;  and  that  rapid  volatilization  takes  place  at  this 
time  is  indicated  by  the  dense  fumes  given  off. 

Importance  of  Temperature. — "As  a  corollary  to  the  fore- 
going, it  follows  that  the  temperature  of  the  pipe,  as  it  emerges 
from  the  bath,  is  one  vital  factor  in  the  character  of  the  coating. 
If  the  pipe  is  too  hot,  the  coating  is  overdistilled  and  becomes 
too  brittle,  or  even  may  be  reduced  to  an  earthy,  carbonaceous 
residuum.  If  the  pipe  is  too  cool,  a  thicker  coating  is  formed, 
which  will  not  harden  sufficiently,  will  come  off  on  the  skids, 
and  will  run  in  warm  weather. 

"At  one  foundry  the  pipes  are  often  wittingly  underheated  on 
days  when  strong  north  winds  prevail,  because  the  wind  makes 
it  difficult  to  heat  the  ovens,  and  the  day's  work  must  be  done 
just  the  same.  Again,  pipes  which  stay  in  the  oven  during  the 
dinner  half -hour  are  liable  to  go  into  the  tank  too  hot,  because 
they  are  left  in  the  oven  too  long  and  are  not  allowed  to  cool 
down.  The  writer  has  often  seen  very  hot  pipes  lowered  into 


264  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

the  tank,  when  they  caused  a  violent  boiling  and  much  yellow 
smoke  (yellow  smoke  is  the  founder's  sign  of  an  excessively  hot 
pipe).  An  inspector  said  that  at  one  foundry  pipes  hot  enough 
to  set  fire  to  the  tar  are  so  common  that  lids  are  rigged  so  that 
they  can  be  rapidly  unhooked  and  allowed  to  fall  over  the  tanks 
and  smother  the  flames. 

"In  general,  the  men  fall  into  a  certain  routine  of  work, — 
so  many  pipes  to  brush  out,  so  many  to  mop  out,  so  many  to 
roll  into  the  oven,  etc.,  between  dippings, — and  this  routine  fixes 
the  time  of  heating.  A  good  dipman  will  not  allow  any  notice- 
able errors  in  temperature  to  pass,  but  he  will  not  delay  the 
routine  for  minor  errors.  In  other  words,  the  application  of 
the  method  is  inferior  to  the  best  judgment  of  the  dipman. 

"  The  character  of  the  tar  in  the  bath  is  another  important 
variable.  New  tar  gives  softer  coatings,  other  things  being  equal, 
because  it  contains  more  of  the  lighter  constituents.  Thick  tar 
gives  thicker  coatings  than  thin  tar.  Fresh  tar  requires  a  hotter 
pipe  than  does  old  tar.  Regularity  in  adding  new  tar  would 
give  greater  uniformity  in  coatings,  but  tar  is  often  not  in  stock 
when  it  is  needed,  and  the  dipman  does  not  care  much,  so  long 
as  the  coating  passes,  and  the  inspectors  do  not  usually  pretend 
to  know  much  about  coatings  or  to  judge  them  very  harshly. 

Dead  Oil. — "Specifications  often  call  for  the  use  of  dead  oil 
of  coal-tar  in  the  dip.  The  misconception  is  probably  often 
entertained  that  dead  oil  bears  to  tar-coating  a  relation  similar 
to  that  of  linseed-oil  in  paint.  A  better  comparison  would  be 
that  between  dead  oil  in  coal-tar  and  turpentine  in  paint.  Dead 
oil  is  of  use  principally  to  thin  back  the  tar  when  it  becomes 
thicker  than  the  dipman  likes  it.  Ordinarily  the  necessary 
adding  of  fresh  tar  is  sufficient  to  keep  the  tar  thin." 

Such  is  the  character  of  the  coating  for  cast-iron  pipes  at 
the  present  time.  All  the  progress  which  has  been  made  in  the 
last  half  century  has  been  in  the  direction  of  cheapening  the 
material  without  regard  to  its  quality,  and  of  simplifying  the 
process  so  as  to  turn  out  a  maximum  amount  of  product  with  a 
minimum  of  plant  and  labor.  The  result  more  than  justifies 


WATER-PIPE  COATING.  265 

Mr.  Wiggin's  remark  that  "perhaps,  if  the  truth  were  known, 
the  modern  crude -tar  coating  would  be  found  to  be  living  on 
the  hard-earned  reputation  of  the  linseed-oil  coating";  and 
this  is  called  the  Angus  Smith  coating,  though  there  can  be  no 
doubt  that  if  he  were  living  he  would  condemn  the  whole  thing 
from  beginning  to  end;  in  fact,  though  the  use  of  his  name  may, 
on  account  of  the  peculiar  wording  of  his  patent  claim,  be  legally 
justified  by  a-  technicality,  it  is%  unfair  treatment  of  the  name 
of  an  able  and  careful  man,  amounting  to  breaking  the  seventh 
and  eighth  commandments,  by  adulterating  his  invention  and 
stealing  his  reputation. 

Coatings  on  cast-iron  pipes  serve  sometimes  another  pur- 
pose. Small  sizes  of  pipe  are  thin,  and  if  the  iron  is  not  of  the 
most  suitable  quality  they  are  liable  to  be  porous.  An  old 
foundryman  who  practised  for  many  years  the  manufacture  of 
small  pipe,  a  man  in  whom  I  have  the  utmost  confidence,  says 
that  when  he  was  making  pipe  it  was  all  tested  by  hydraulic 
pressure,  and  new  pipe  was  very  frequently  leaky,  by  reason 
of  minute  sand- holes.  This  was  in  Wisconsin,  and  gas- tar  was 
unknown  at  that  time  in  that  part  of  the  country;  so  the  pipe 
was  put  in  a  bath  of  strong  salt  water  for  twelve  hours  and  then 
exposed  to  the  air  for  a  few  days,  when  it  was  found  to  be  per- 
fectly tight,  the  openings  having  been  closed  with  rust.  Obvi- 
ously a  coal-tar  dip  would  accomplish  the  same  result.  This  is 
in  line  with  the  current  practice  of  shop-painting  corrugated  sheet 
iron,  which  is  often  so  full  of  pin-holes  as  to  be  unsalable  unless 
it  is  painted.  The  paint  usually  applied  to  corrugated  iron  is 
more  expensive  than  coal-tar,  costing  about  twenty  or  twenty^five 
cents  per  gallon. 

Tar  Not  Used  on  Steel  Pipe. — It  has  always  been  recognized 
that  a  coal-tar  coating  is  not  good  enough  to  be  of  use  on  steel 
riveted  pipes,  or  on  steel  or  iron  welded  pipes.  Very  large  pipes 
are  usually  made  of  steel  plates  rolled  to  the  desired  form  and 
riveted,  the  operation  of  making  them  being  practically  like 
making  the  shell  of  a  steam-boiler.  These  pipes  are  commonly 
made  up  in  three  sheet  sections,  25  to  30  feet  long;  these  are 


266  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

coated  and  then  are  shipped  to  the  point  where  they  are  to  be 
laid.  The  steel  sheets  are  received  at  the  shop  in  most  cases 
perfectly  clean  and  free  from  dust,  their  surfaces  being  covered 
with  blue  mill-scale  very  thin  and  adherent.  When  these  are 
passed  through  the  bending-rolls  they  are  of  course  put  under  a 
strain,  for  sheets  a  quarter  to  a  half  inch  in  thickness  do  not  bend 
very  easily,  and  this  breaks  loose  all  the  scale  which  is  at  all  dis- 
posed to  come  off,  so  that  even  without  pickling  or  sand-blasting 
the  surface  is  really  in  very  good  condition,  not  of  course  as  good 
as  if  entirely  freed  from  scale,  but  much  better  than  that  of  any 
other  structural  work  in  its  natural  state. 

Dipping  in  Asphaltum. — These  sections  are  then  heated  and 
dipped  into  a  vat  of  coating  material,  which  is  also  hot;  usually 
this  is  a  horizontal  vat,  and  the  pipe  is  rolled  into  it  and  rolled 
over  in  it  by  means  of  chains  which  go  around  the  pipe  and  which 
form  a  sling  for  handling  it;  the  pipe  is  then  lifted  from  the  vat, 
not  quite  in  a  horizontal  position,  but  with  its  axis  inclined  ten  or 
twenty  degrees,  and  the  surplus  coating  runs  out  of  the  interior 
and  off  from  the  outside  back  into  the  tank.  It  is  held  thus  over  the 
hot  tank,  the  heat  from  which  promotes  the  draining,  until  it  ceases 
to  drip ;  then  it  is  removed  and  allowed  to  cool.  The  coating  com- 
pound is  a  soft  asphaltum,  made  softer  than  its  natural  state  by  the 
addition  of  mineral-oil  residues  of  high  boiling-point ;  as  this  oily 
matter  gradually  evaporates  out  it  is  replaced  by  further  additions 
from  time  to  time.  Much  of  this  pipe-coating  material  is  known 
as  maltha,  and  is  separated  from  California  petroleum  as  a  residue 
left  in  the  retort  after  distilling  off  the  more  volatile  portions  of 
the  natural  oil.  The  longer  this  process  of  distillation  is  carried 
on  the  thicker  and  harder  will  be  the  residue;  so  the  maker  pre- 
pares two  kinds,  one  of  which  is  perhaps  a  little  too  hard  for  use 
by  itself  and  the  other  much  softer,  and  by  mixing  these  the 
dipman  can  get  a  compound  of  any  desired  degree  of  hardness. 

Various  Kinds  of  Asphaltum. — Asphaltum  is  the  name  of 
a  class  of  minerals  related  to  petroleum-oil,  from  which  geolo- 
gists think  it  is  derived.  Petroleum,  according  to  Dana,  passes  by 
insensible  graduations  into  maltha,  and  the  latter  as  insensibly 


WATER-PIPE  COATING.  267 

into  solid  bitumen;  some  of  the  solid  asphalts,  such  as  Trinidad, 
while  hard  enough  to  be  brittle  when  struck  are  soft  enough  to  be 
viscous  and  flow  under  long-continued  pressure;  the  more  fluid 
of  these  cannot  freely  be  made  to  unite  with  linseed-oil.  From 
these  we  gradually  pass  to  gilsonite,  a  much  harder  substance, 
which  shows  no  viscosity  at  natural  temperatures,  but  is  yet 
perfectly  fusible  and  is  called  by  mineralogists  a  resinous  mineral 
or  a  mineral  resin.  It  is  nearly  free  from  mineral  oily  matter  and 
hence  unites  readily  with  vegetable  oils ;  and  we  may  pass  beyond 
this  to  the  mineral  known  as  albertite,  which  is  almost  or  quite 
infusible  and  differs  from  bituminous  coal  chiefly  in  structure 
and  in  the  nature  of  the  products  of  decomposition  obtained 
when  it  is  subjected  to  intense  heat.  This  latter  does  not  soften 
with  oil  and  is  of  no  interest  in  this  connection.  The  semi-fluid 
and  tarlike  bitumens  are  known  by  the  name  of  maltha,  an  old 
Greek  name  applied  to  these  substances  by  Pliny,  and  still  used 
with  that  meaning;  and,  as  has  been  said,  it  is  also  applied  to 
the  bitumens  artificially  prepared  from  petroleum,  especially  the 
dense  and  bitumen-bearing  sort  found  in  California.  Maltha 
greatly  resembles  in  appearance  coal-tar  or  coal-tar  pitch,  but  is 
very  different  in  its  chemical  properties,  and  the  one  cannot  be 
substituted  for  the  other. 

Defects  in  This  Coating. — When  pipe  sections  have  been  coated 
in  the  way  described,  it  will  be  easily  understood  that  the  com- 
pound runs  off  more  from  that  side  of  the  pipe  which  chances  to 
be  uppermost  while  the  pipe  is  being  held  in  its  approximately 
horizontal  position  to  drain,  and  will  be  thickest  on  the  opposite 
side;  alike  on  the  interior  and  exterior  of  the  pipe.  Usually  it 
runs  off  until  there  is  a  thickness  on  the  thin  portions  of  ^  to  7V 
of  an  inch;  on  the  thicker  portions,  it  may  be  TV  to  J  of  an  inch; 
but  it  is  not  uncommon  to  find  pipe  sections  with  a  thickness  of 
i  or  2  ins.  of  coating  along  the  side  which  was  the  bottom  when 
the  pipe  was  draining.  The  compound  is  heated  in  the  dipping- 
tank  to  about  300°  or  350°  F.,  and  the  mineral  oil,  which  is  the 
softening  ingredient,  constantly  distils  off,  so  that  the  composition 
continually  changes,  and  no  two  successive  pipe  sections  are 


268  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

coated  alike.  When  the  mixture  gets  so  viscid  that  it  will  not  run 
off  the  pipe  with  what  the  dipman  regards  as  reasonable  freedom, 
he  adds  a  barrel  or  so  of  thinning  compound,  and  the  next  few 
pipes  get  a  coating  as  much  too  thin  as  that  on  the  preceding  ones 
was  too  thick.  The  specifications  usually  say  that  the  compound 
shall  be  of  such  a  nature  that  it  shall  not  be  brittle  in  cold  weather 
nor  run  or  be  sticky  in  hot  weather;  as  a  matter  of  fact,  it  is 
brittle  under  a  blow  always,  and  in  hot  weather  masses  of  it 
weighing  several  pounds  will  slide  off  the  outside;  and  on  the 
inside,  where  the  pipe  lies  so  that  the  thickest  part  of  the  coating 
is  at  the  top,  it  runs  down  in  stalactitic  forms,  sometimes  extend- 
ing across  the  whole  diameter  of  the  pipe;  and  I  know  of  places 
where  workmen  had  to  be  sent  through  the  pipe  to  break  out 
these  obstructions.  Asphalt  compounds  of  this  sort  are,  at 
ordinary  temperatures,  fairly  hard  to  the  touch,  and  if  struck 
with  a  hammer  are  more  or  less  brittle,  yet  they  yield  to  gentle 
continued  pressure.  If  they  can  be  got  into  service  without  injury 
they  last  a  long  time,  because  they  are  perfectly  impervious  to 
water,  and  are  only  destroyed  gradually  from  the  surface,  not  all 
at  once  throughout  their  whole  thickness  as  a  porous  substance 
would  be ;  and  as  they  are  buried  in  the  earth  and  filled  with 
water  they  change  temperature  but  little  and  that  little  with 
almost  inconceivable  slowness,  so  that  they  do  not  crack  with 
changes  of  temperature.  The  thicker  such  a  coating  is  the  longer 
it  is  likely  to  last  after  once  it  gets  into  service;  but  the  thicker 
it  is  the  more  difficult  it  is  to  handle  during  the  three  to  six  months, 
or  sometimes  more,  which  elapse  between  the  time  of  coating  and 
the  testing  of  the  line,  after  which  it  can  be  covered  with  earth. 
Before  that  time  it  is  subject  to  misuse  of  more  sorts  than  the 
inexperienced  reader  can  imagine. 

Handling  of  Pipe. — Usually  it  is  loaded  on  open  railway-cars, 
on  which  it  is  piled  up,  one  section  on  the  top  of  another,  and  the 
rivet-heads  dig  holes  in  the  coating;  but  sometimes  this  is  in 
part  prevented  by  laying  old  rope  or  other  packing  material  be- 
tween the  pipes.  The  posts  on  the  sides  of  the  car  scrape  off  some 
during  transit;  and  when  it  arrives  at  the  point  of  destination  by 


WATER-PIPE  COATING.  269 

rail  the  pipe  is  rolled  off  the  car  without  very  much  ceremony; 
sometimes  it  rests  on  skids,  sometimes  on  the  ground.  After  it 
has  been  there  a  few  days  or  weeks,  during  which  time  boys  pelt 
it  with  stones  and  hammer  it  with  cudgels  to  hear  the  pleasing 
and  resonant  sound  it  emits,  and  play  hide-and-seek  in  it,  it  is 
loaded  on  farm  wagons  and  hauled  over  country  roads  and  across 
fields,  sometimes  as  far  as  fifteen  miles,  and  dumped  by  the  side 
of  the  ditch  on  the  gravel  and  loose  stones  which  have  been  exca- 
vated; then  it  is  partly  slid  and  partly  lowered  into  the  ditch. 
There  one  might  suppose  it 

"...  sleeps  well. 

Malice  domestic,  foreign  levy,  nothing 
Can  touch  him  further." 

Not  yet.  The  sides  of  the  ditch  are  covered  with  fresh  earth, 
poor  walking  in  dry  weather  and  banks  of  mud  when  it  rains; 
but  the  pipe  lying  in  the  ditch  makes  a  beautiful  asphalt  walk, 
and  is  used  as  such  not  only  by  the  curious  rustic  and  the  casual 
visitor  but  also  by  the  entire  gang  of  laborers  going  to  and  return- 
ing from  work.  Thus  a  large  part  of  the  coating  on  the  outside 
of  the  top  is  removed;  and  if  it  is  at  all  brittle,  on  cool  mornings 
the  vibration  from  people  walking  over  it  cracks  it  off  from  the 
inside  of  the  upper  segment.  This  kind  of  thing  may  be  called 
the  "malice  domestic."  Then  comes  the  "foreign  levy"  in  the 
shape  of  a  gang  of  tramp  riveters  to  do  the  field  riveting.  They 
are  armed  with  sledges,  hammers,  crowbars,  and  chisels;  part 
of  them  work  inside  the  pipe  and  part  on  the  outside.  They  wear 
hob-nailed  shoes;  their  sensibilities  are  not  attuned  to  the  high- 
est pitch  of  refinement.  The  pipe  had  a  good  coating  to  start  with 
if  there  is  much  left  on  it  when  they  get  through.  And  over  all 
arches  the  clear  blue  sky,  from  which  the  July  sun  shines  down, 
and  its  heat  is  reflected  from  the  yellow  sides  of  the  ditch,  and  is 
absorbed  by  the  black  pipe  until  it  is  so  hot  that  one  cannot  hold 
the  hand  on  it,  and  if  the  coating  is  at  all  viscous  it  softens  and 
slides  off  from  the  outside,  and  on  the  inside  forms  great  tears 
and  stalactite  shapes.  Then  it  rains,  and  all  the  bare  places,  in- 
side and  out,  get  rusty.  And  the  chief  engineer  objurgates  and 


27°  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

deplores,  and  when  he  wants  sympathy  has  to  look  for  it  in  the 
dictionary. 

Repairs. — These  defective  places  in  the  coating  are  repaired 
by  painting.  Long  before  the  experiments  on  paints  and  var- 
nishes'described '  in  the  previous  chapter  Were  made,  the  water- 
works engineers  had  found  out  that  no  reliance  could  be  placed 
on  oil  and  pigment  paints  for  hydraulic  work;  and  the  coating 
most  commonly  applied  is  a  sort  of  spirit  varnish,  made  of  the 
same  asphalt  compound  used  in  dipping  the  pipes,  dissolved  in 
some  volatile  solvent  either  turpentine,  benzine,  or  bisulphide  of 
carbon.  All  these  form  inflammable  vapors  which  are  explosive 
when  mixed  with  air,  hence  incandescent  electric  lights,  the  wires 
of  which  are  most  carefully  insulated,  are  the  only  source  of  light 
which  should  be  used;  and  as  these  vapors  are  unhealthful,  and 
that  of  carbon  disulphide  in  particular  is  extremely  poisonous, 
the  pipe  should  be  ventilated  by  blowing  a  steady  blast  of  air 
through  it  from  the  direction  from  which  the  painters  enter  the 
pipe,  so  as  to  blow  against  their  backs  and  always  carry  the  gases 
from  them.  This  is  a  precaution  which  should  never  for  a 
moment  be  omitted;  men  have  lost  their  lives  or  become  insane 
from  inhaling  some  of  these  gases. 

If  the  varnish  thus  applied  does  not  make  a  very  thick  coat, 
two  or  three  coats  should  be  used;  the  more  the  better,  for  the 
pipe  will  never  again  be  so  accessible.  It  is  possible  at  this  time 
to  use  an  elastic  oleo-resinous  varnish,  one  containing  asphaltum, 
and  this  is,  in  my  judgment,  the  best  thing  to  use,  but  it  is  slow 
to  dry  unless  a  current  of  air  is  passing  through  the  pipe,  which 
is  often  the  case.  Not  less  than  two  coats  of  such  a  varnish 
should  be  used.  On  the  outside  of  the  pipe  it  is  often  possible 
to  apply  some  of  the  hot,  melted  compound,  such  as  was  used  in 
the  dipping-vat;  it  may  be  melted  by  the  side  of  the  ditch  in  a 
kettle  and  applied  with  a  swab  or  brush,  or  sometimes  poured  on 
from  a  ladle. 

Corrugations. — Pipes  coated  in  this  manner  frequently,  per- 
haps I  may  say  commonly,  exhibit  ridges  and  furrows  occasioned 
by  the  irregularities  of  flow  of  the  compound  while  draining;  the 


Laying  Water-mains  of  40-  and  38-inch  Steel  Enamelled  Pipe 


..ITY 


WATER-PIPE  COATING. 


271 


accompanying  illustrations  show  the  character  of  these,  both  on 
the  outside  and  inside  of  the  pipe.    On  the  outside  they  do  little 


harm;  on  the  inside  they  seriously  diminish  the  flow  of  water  by 
causing  eddies  and  irregular  currents. 


272  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

Vertical  Dipping-tank. — An  attempt  has  been  made  to  im- 
prove on  this  method  of  dipping  by  using  a  vertical  tank  in  which 
the  pipe  section  is. entirely  immersed;  it  is  then  slowly  lifted,  end- 
ways of  course,  and  as  the  lower  end  of  the  pipe  is  in  the  liquid, 
the  cold  air  cannot  get  in,  and  so  the  compound  does  not  chill,  but 
runs  of!  smoothly,  from  the  inside;  and  this  improvement  makes 
it  possible  to  use  a  compound  which  has  a  much  higher  melting- 
point  than  that  used  in  the  horizontal  dipping-tank,  which  will  in 
consequence  be  unaffected  by  the  heat  of  the  sun.     Such  com- 
pounds have  been  made ;  I  do  not  know  their  composition,  but  I 
imagine  from  a  rather  hard  asphalt,  perhaps  from  "gilsonite 
seconds,"    inferior  gilsonite  from  that   part  of   the    deposit  of 
mineral  which  has  been  exposed  to  the  weather,  softened  with  a 
very  thick  and  heavy  mineral  lubricating  oil  from  which  all  the 
products  except  those  of  very  high  boiling-point  have  been  dis- 
tilled.    These  compounds  have  a  considerable  degree  of  tough- 
ness even  when  quite  cold,  and  stand  transportation  and  rough 
handling  very  much  better  than  the  ordinary  coating,  such  as  has 
been  described.     The  temperature  of  the  dip  is  about  400°  F., 
and  the  compound  sets  and  ceases  to  run  on  the  outside  of  the 
pipe  while  still  far  too  hot  to  be  touched  by  the  hand ;  it  does  not 
flow  off  well  from  the  exterior  surface,  and  men  stand  around  the 
mouth  of  the  tank  when  the  pipe  is  being  hoisted  out  with  scrapers 
and  scrape  off  as  much  as  they  can  from  the  surface  back  into 
the  tank.     The  compound  sets  so  rapidly  that  itvis  often  possible 
to  see  the  marks  of  these  scrapers  on  the  finished  pipe.     I  think 
they  are  liable  to  scrape  it  off  too  closely,  leaving  too  thin  a  coat- 
ing on  the  outside.    I  have  myself  seen  sections  of  such  coated 
pipe  which  had  been  exposed  to  the  weather  for  a  few  weeks  which 
had  considerable  areas  of  coating  so  thin  that  in  a  favorable  light 
I  could  see  the  metal  through  the  coating;  and  where  the  weather 
had  removed  the  elastic  ingredient  from  the  superficial  layer  I 
could  with  my  finger  rub  off  all  the  coating  and  expose  the  clean 
metal;  the  coating,  being  extremely  thin,  had  become  earthy  and 
friable,  and  could  be  easily  rubbed  off  by  friction.     Of  course 
such  a  coating  was  no  protection;   but  the  inside  of  these  same 


WATER-PIPE   COATING.  273 

pipes  was  well  and  uniformly  coated  and  most  of  the  outside  had 
a  fair  coat.  A  coating  of  this  sort,  if  properly  applied,  ought  to 
give  good  service.  Its  principal  defect,  which  it  shares  with  the 
asphalt  dip  previously  described,  is  that  the  elastic  ingredient  is  a 
mineral  oil  which  becomes  lost  by  diffusion,  and  leaves  the  asphalt, 
or  rather  the  asphaltene  part  of  the  asphalt,  in  an  earthy  and  fri- 
able condition ;  this  action  takes  place  from  the  surface  and  con- 
sequently does  not  rapidly  produce  a  decomposition  of  the  coating 
as  a  whole,  but  it- is  progressive  and  is  the  principal  cause  of  the 
failure  of  asphalt  coatings,  which  after  a  long  time  become  earthy 
and  lose  their  coherence  throughout  and  cease  to  afford  protec- 
tion; and  long  before  they  reach  this  stage  the  deterioration  of 
the  surface  makes  it  a  suitable  foothold  for  algae  and  other  aquatic 
growths.  I  suppose  that  a  compound  could  be  made  of  asphaltum 
tempered  with  linseed-oil  which  would  be  much  better,  but  it 
would  be  costly  and  has  never  been  attempted. 

Varnish  Enamels. — The  oldest  varnish-makers  and  users  of 
whom  we  have  any  definite  record,  artisans  of  the  tenth  to  the 
fifteenth  centuries,  knew  that  varnish  applied  to  metal  and  then 
hardened  by  baking  made  a  coating  of  great  durability.  This 
probably  was  discovered  by  observing  that  the  more  elastic 
varnishes  are  the  more  durable,  and  then  that  these  varnishes, 
which  contain  a  large  proportion  of  oil,  are  slow  to  dry,  and 
not  very  hard  when  they  are  dry.  No  doubt  varnishes  were  in 
those  days  much  slower  than  are  those  of  approximately  the  same 
composition  to-day,  because  they  did  not  understand  the  refining 
of  oil  as  well  as  we  do,  nor  was  their  knowledge  of  varnish-making 
in  its  details  to  be  compared  with  ours.  But  human  nature 
has  been  about  the  same,  and  when  a  knight  got  a  new  sword-hilt 
he  probably  did  not  bring  it  in  to  be  enamelled  until  the  day 
before  the  tournament,  and  had  to  have  it  back  that  same  after- 
noon. Thus  the  enameller,  although  he  was  ignorant  of  the  fact 
that  the  activity  of  the  ions  was  augmented  by  an  increase  in 
temperature,  learned  to  observe  that  varnish  dried  more  quickly 
if  exposed  to  heat,  and  he  put  the  varnished  hilt  in  the  oven  and 
baked  it  for  two  or  three  hours,  and  everything  was  satisfactory. 


274  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

The  materials  were  not  very  costly  and  the  process  was  simple, 
so  that  all  sorts  of  small  metal  objects  were  treated  in  this  way, 
not  only  for  ornament,  but  for  common  use;  and  the  practical 
details  were  well  understood  long  before  any  one  cared  about 
the  theory  of  the  matter. 

The  Rochester  Pipe-line.  —  Only  small  things  were  treated 
in  this  way.  When  freshly  varnished  objects  are  put  into  an 
oven  the  volatile  solvent,  turpentine  or  benzine,  is  quickly  evapo- 
rated, and  this  causes  danger  of  fire;  and  this  has  the  effect  of 
prohibiting  such  work  on  a  large  scale;  but  when,  in  1893,  I 
was  applied  to  by  the  authorities  of  the  city  of  Rochester,  N.  Y., 
for  advice  as  to  the  best  way  of  preserving  their  new  water-main 
from  corrosion,  I  decided  that  this  must  be  the  process,  and 
that  it  must  be  so  modified  as  to  make  it  practicable.  The  pipe  in 
question  was  an  intake  from  Hemlock  Lake,  and  was  for  most 
of  its  length  a  38- in.  steel  riveted  pipe;  the  coating  was  the  com- 
mon asphalt  or  maltha  dip,  and  was  not  satisfactory,  for  the 
reasons  which  have  been  indicated  -  in  the  foregoing  account  of 
that  process.  It  seemed  to  me  that  the  best  coating  which  could 
be  applied  would  be  a  true  varnish  enamel.  While  it  was  true 
that  fairly  satisfactory  results  had  been  obtained  on  cast-iron 
pipe  by  Dr.  L.  Angus  Smith  with  a  sort  of  an  enamel  of  coal- 
tar  pitch  and  linseed-oil,  this  could  not  be  depended  on  for  steel 
pipe,  for  the  following  reasons: 

The  R.  Angus  Smith  Process  Not  Suited  to  Steel  Pipe. — In 
the  first  place,  the  Smith  coating  was  baked  on  by  the  residual 
heat  in  the  pipe  after  coming  out  of  the  dip;  this  could  be  done 
because  the  weight  of  metal  was  very  great,  but  steel  pipe  is  thin 
and  does  not  hold  much  heat.  Second,  it  was  not  a  rational 
method.  As  has  been  seen,  the  pipe  was  first  dipped  in  pure  oil, 
then  baked,  then  again  dipped  in  an  oil  and  pitch  compound, 
then  rinsed  off  with  oil,  and  the  final  baking  was  partly  a  process 
of  oxidizing  the  oil  and  partly  hardening  the  pitch  by  evaporat- 
ing its  volatile  constituents,  which,  however,  could  have  been 
present  in  only  small  amounts.  The  final  result  would,  of  course, 
depend  on  the  proportion  of  oil  in  the  coating,  which  must  have 


WATER-PIPE  COATING.  275 

been  quite  variable,  and  the  thickness,  and  consequent  rate  of 
cooling,  of  the  pipe.  The  pipe  was  not  coated  with  a  definite 
compound;  and  the  oil  and  pitch  were  not  united  by  cooking 
together,  as  is  the  practice  of  the  varnish- maker.  Third,  it 
was  expensive;  the  pipe  practically  had  two  coatings,  one  of 
oil  and  one  of  the  indeterminate  mixture,  and  the  results  would 
depend  on  the  skill  of  the  operator  in  a  rather  excessive  degree. 
Fourth,  cast-iron  pipe  does  not  need  such  perfect  protection 
as  steel  pipe,  as  it  is  not  so  much  inclined  to  rust  and  is  much 
thicker,  and  a  coating  which  might  answer  for  one  would  not 
do  for  the  other,  as  in  fact  was  agreed  by  everybody,  and  the 
modern  coal-tar  coating  was  not  to  be  considered.  But  asphaltum 
is  a  substance  which  can  be  had  of  a  definite  composition  and 
character,  in  any  quantity  desired,  and  it  is  greatly  superior  in 
every  way  to  coal-tar  pitch;  and  if  the  pipe  were  baked  in  an 
oven  it  could  be  exposed  for  any  desirable  period  to  any  desired 
temperature;  hence  we  can  not  only  temper  the  coating  com- 
pound with  just  enough  oil  to  make  it  slightly  tough,  but  can 
put  in  all  the  oil  we  need  to  give  it  any  desired  degree  of  elasticity, 
because  we  will  leave  the  coated  pipe  in  the  oven  until  the  coating 
is  perfectly  and  exactly  oxidized.  Besides  all  this,  the  coating  thus 
applied  is  thin  and  hence  much  less  costly  than  it  would  be  if  as 
thick  as  a  common  asphalt  dip,  so  that  in  making  such  an  enamel 
we  are  not  restricted  by  cost  to  asphaltum  for  a  resinous  ingredi- 
ent, but  can  use  in  addition  any  other  resins  of  low  price,  and 
some  of  the  low-priced  varnish  resins  are  of  a  high  degree  of 
excellence  in  everything  except  color,  and  the  oil  can  be  properly 
refined,  and  the  compound  made  up  according  to  the  best  knowl- 
edge of  the  varnish-maker. 

The  Sabin  Process. — The  danger  of  fire  was  avoided  by 
the  simple  means  of  leaving  the  turpentine  or  benzine  out  entirely; 
the  compound  was  of  course  thick  and  stiff  at  ordinary  tem- 
peratures, but  by  heating  it  in  a  tank  to  about  300°  F.  it  be- 
came fluid,  and  was  applied  by  dipping  the  object  to  be  coated 
in  it,  precisely  as  though  it  were  an  asphalt  or  a  coal-tar  dip. 
After  dipping  the  pipe  was  at  once  put  in  a  suitable  oven  and 


276  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

baked  until  the  coating  was  properly  oxidized.  Of  course,  such 
a  compound  and  such  a  process  were  far  more  expensive  than 
the  coal-tar  dip  as  used  on  cast-iron  pipes;  but  that  had  nothing 
to  do  with  the  question.  It  was  not  excessively  costly  as  com- 
pared with  a  good  asphalt  dip,  nor  in  fact  very  much  more  so; 
and  it  was  not  a  matter  of  stopping  up  sand-holes,  nor  of  making 
the  pipe  look  as  though  it  had  been  coated,  but  of  securirg  a 
really  adherent  and  preservative  film  which  would  endure  toler- 
ably well  the  unavoidable  rough  handling  which  sections  of 
water-pipe  receive.  About  14  miles  of  38-in.  steel  pipe  was 
coated  in  this  manner  for  this  Rochester  conduit,  and  the  work 
was  done  with  remarkable  uniformity.  Considering  the  fact  that 
this  was  the  first  attempt  to  coat  large  work  of  any  sort  in  this 
way  and  that  the  apparatus  and  process  of  handling  were  in  a 
large  degree  experimental,  the  uniform  and  excellent  results 
obtained  not  only  reflect  credit  on  the  operators  but  show  that 
the  process  must  be  in  its  nature  reasonably  simple  and  easy  to- 
conduct.  The  pipe  sections  were  28  feet  long  and  weighed  about 
2  tons  each,  part  of  them  2\  tons;  they  were  after  coating  trans- 
ported on  wagons  to  the  place  of  use,  the  distance  being  in  some 
cases  14  miles,  over  very  ordinary  roads;  and  it  was  the  general 
opinion  of  all  who  saw  the  work  that  the  coating  stood  the  neces- 
sary handling  extremely  well.  Of  course,  the  rivets  of  the  field- 
riveted  joints  had  nothing  on  them,  and  their  heat  destroyed 
the  coating  with  which  they  came  in  immediate  contact;  but 
these  places  were  painted  with  an  air-drying  varnish  of  com- 
position similar  to  that  of  the  baked  coating,  as  were  also  all 
spots  from  which  the  coating  had  been  abraded,  which  were, 
however,  very  few  and  small;  for  not  only  does  such  a  coating 
stand  hard  usage  well,  but  on  account  of  its  beauty  and  apparent 
delicacy  it  actually  gets  much  more  careful  treatment  from  the 
workmen  than  does  a  coarser  and  rougher  one. 

Character  of  the  Coating. — A  coating  of  this  kind  is  hard 
and  elastic  enough  to  stand  a  smart  blow  with  a  hammer  with- 
out injury,  but  anything  can,  by  the  application  of  sufficient 
force,  be  scraped  off  any  metallic  surface.  It  is,  however,  a 


l/N/y, 


Laying  Water-mains  of  40-  and  6o-inch  Steel  Enamelled  Pipe. 


WATER-PIPE  COATING.  277 

mistake  to  compare  a  pipe -line  to  a  chain,  whose  strength  is 
that  of  its  weakest  link,  and  say  that  its  protection  is  measured 
by  that  of  the  least  protected  spot;  if  this  were  so,  there  would 
be  no  water-pipes  in  use. 

Corrosion  is  Local. — As  a  matter  of  fact  corrosion  is  not  uniform 
and  general,  but  local;  and  if  99  per  cent,  of  the  surface  is  pro- 
tected the  durability  of  the  pipe  is  probably  increased  at  least 
90  per  cent.  I  have  seen  old  pipe  with  practically  no  coating 
removed  from  a  bed  of  blue  clay  without  the  least  rust  on  it ;  but 
we  must  remember  that  the  coloring-matter  of  clay  is  iron,  and 
in  blue  clay  it  is  in  the  ferrous  condition,  not  saturated  with  oxygen ; 
when  we  burn  blue  clay  it  becomes  red  because  the  iron  in  it 
becomes  more  highly  oxidized.  Hence  it  is  plain  that  blue  clay 
may  act  as  a  reducing  agent,  net  as  an  oxidizing  one,  and  tends 
to  abstract  oxygen  from  anything  with  which  it  is  in  contact;  'and 
it  is  well  known  that  peat  does  the  same  thing.  So  it  is  that  in 
one  place  a  pipe  may  tend  to  rust  and  in  another  it  will  be 
preserved,  independently  of  the  effect  of  a  coating;  and  the 
fact  that  we  cannot  attain  absolute  perfection  in  a  pipe  coating  is 
no  reason  why  we  should  not  apply  as  good  a  protection  as  is 
available. 

The  Allegheny  and  Cambridge  Lines. — Owing  to  the  impor- 
tance of  the  subject,  the  novelty  of  the  method  employed,  and  in 
no  small  part  the  high  reputation  of  the  engineer  in  charge  (Mr. 
Emil  Kuichling),  this  Rochester  pipe-line  attracted  a  great  deal 
of  attention;  and  a  similar  coating  was  applied,  the  year  after 
this  was  finished,  to  the  pipe-line  at  Allegheny,  Pa.,  which  was 
nearly  10  miles  in  length  and  5  feet  in  diameter, — at  the  time, 
I  believe,  the  largest  pipe-line  in  the  world, — and  to  a  conduit  in 
Cambridge,  Mass.,  about  4^  miles  long  and  40  inches  in  diameter. 
The  pipe  sections  at  Cambridge  were  of  about  the  same  dimen- 
sions as  those  at  Rochester;  for  the  Allegheny  pipe  they  were  only 
25  feet  long,  but  as  they  were  60  inches  in  diameter,  and  the  steel 
plate  of  which  they  were  made  was  \  inch  in  thickness,  they 
weighed  5  tons  each.  The  oven  constructed  for  handling  these 
enormous  pipes  had  a  capacity  of  eight  sections,  and  was  divided 


•278  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

into  four  parts,  so  that  one  part  of  the  oven  could  be  opened  with- 
out cooling  off  the  other  three.  Two  hours  was  required  for 
baking  and  about  an  hour  was  used  in  charging  and  emptying 
the  oven,  so  that  eight  pipe  sections  could  be  baked  every  three 
hours,  or  the  oven  could  be  charged  and  emptied  eight  times  in 
twenty-four  hours;  or  sixty-four  sections  a  day,  equal  to  320 
tons;  and  this  was  actually  accomplished.  When  finished,  the 
pipes  were  tested  by  pounding  them  at  intervals  of  a  foot  or  two 
with  a  J-in.  steel  rod,  and  if  any  of  the  coating  could  thus  be 
loosened  it  was  rejected ;  but  it  was  necessary  to  recoat  only  a  few 
of  these  sections,  perhaps  a  dozen  out  of  the  nearly  2000  which 
were  made.  Since  then  this  process  has  been  applied  to  ordi- 
nary small  sizes  of  steam-pipe,  for  electric  conduits,  and  other 
uses,  and  I  have  seen  J-in.  pipe  which  had  been  coated  bent 
around  a  post  into  a  coil  with  an  internal  diameter  of  about  8 
inches,  without  cracking  the  coating,  which  was  so  hard  that  it 
could  not  be  scratched  with  the -thumb-nail;  and  in  one  estab- 
lishment as  high  as  28,000  linear  feet  of  pipe  has  been  coated 
per  day. 

Used  in  the  U.  S.  Navy. — Not  long  after  the  completion  of 
the  work  which  has  been  described  the  Bureau  of  Construction 
and  Repair  of  the  U.  S.  Navy  Department  built  a  coating  plant 
for  using  this  compound,  which  by  this  time  had  become  known 
by  the  name  of  the  Sabin  compound  (and  the  method  as  the 
Sab  in  process),  in  the  New  York  Navy  Yard  at  Brooklyn.  The 
especial  use  to  which  the  naval  authorities  put  it  is  for  the  pro- 
tection of  fire-mains  and  flushing-mains  on  board  ships.  The 
former  of  these  in  particular  have  been  a  source  of  a  great  deal 
of  trouble.  Although  made  of  heavy  copper  of  the  best  quality 
they  rapidly  corrode,  not  uniformly,  but  holes  appear,  the  cor- 
rosion taking  place  from  the  inside,  which  is  filled  with  sea- 
water  under  a  pressure  of  100  to  150  Ibs.  to  the  square  inch. 
These  pipes  sometimes  last  only  two  months,  rarely  twelve,  and 
formerly  had  an  average  life  of  about  six  months.  Since  using 
this  coating  they  have  lasted  three  and  four  years,  and  their 
ultimate  durability  is  not  yet  determined.  This  coating  is, 


WATER-PIPE  COATING.  279 

consequently,  specified  on  all  war-ships ;  and  at  most  of  the  navy 
yards  and  at  several  private  yards  plants  for  its  application  have 
been  constructed. 

It  may  here  be  said  that  in  1903-4  the  steel  underfloors  of  the 
roadways  and  sidewalks  of  the  Williamsburg  Bridge  over  the 
East  River  in  New  York  City  were  pickled  and  coated  by  this 
process  in  a  manner  quite  satisfactory  to  the  engineers  in  charge, 
and  that  this  was  the  second  lot  of  structural  steel  (except  for 
ship-building)  to  be  pickled  in  this  country;  undoubtedly  the 
first  to  be  pickled,  dipped,  and  baked  in  any  country. 

The  proper  application  of  such  a  coating  requires  a  film  of 
uniform  thickness  to  be  spread  over  the  surface  of  the  metal,  and 
that  this  should  be  oxidized  to  a  certain  normal  point  correspond- 
ing to  the  complete  and  perfect  oxidation  of  linseed-oil  to  linoxyn, 
or  "oil-rubber";  but  the  oxidation  should  not  be  carried  beyond 
this  point,  or  the  coating  will  lose  its  elasticity,  and,  if  carried 
much  beyond  it,  its  adhesiveness  to  the  metal.     In  order  to  get 
this  uniform  film,  the  object  to  be  coated  is  thoroughly  cleaned, 
heated  a  few  minutes  in  a  hot  oven,  and  dipped  in  the  hot  com- 
pound.    It  is  well  known  that  all  metallic  surfaces  have  nor- 
mally an  adherent  film  of  air,  which  is  removed  only  with  diffi- 
culty, and  the  easiest  way  to  break  up  this  adhesion  is  to  heat  the 
metal.    The   hot   liquid,   therefore,   wets   the   hot   metal   much 
more  readily  and  perfectly  than  a  cold  liquid  will  wet  a  cold 
metal;  and  as  the  heat  is  maintained  for  a  considerable  time  the 
liquid  gradually  crawls  over  any  minute  uncovered  portions  and 
in  this  way  a  perfect  and  continuous  contact  between  the  metal 
and  the  coating  is  established.    This  is  promoted  by  the  strong 
capillary  attraction  which  exists  between  the  compound  and  the 
surface  of  the  metal,  especially  if  the  latter  is  iron  or  steel;  much 
less  attraction  seems  to  be  manifested  between  the  compound 
and  zinc,  brass,  or  even  copper,  although  the  latter  two  are  con- 
stantly being  coated  at  the  Navy  Yard  plants. 

Details  of  the  Process. — The  object  to  be  coated  is  left  in  the 
dipping-tank  two  or  three  minutes,  then  taken  out,  held  over  it  to 
drain  for  a  short  time  until  the  greater  part  has  run  off,  but  not 


280  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

until  the  compound  appears  to  be  thickening  with  cold,  then  put 
in  the  hot  oven.  Ordinarily  about  twice  as  much  compound  will 
adhere  to  the  object  as  is  need.ul  to  form  the  coating.  The  sur- 
plus runs  off  and  is  caught  in  a  convenient  receptacle,  from  which 
it  is  returned  to  the  dipping-tank.  If  it  were  left  in  the  oven  it 
would  be  wasted,  and  would,  moreover,  be  carbonized  and  fill  the 
oven  with  smoke,  to  the  injury  of  the  coating.  Commonly  it  takes 
from  fifteen  minutes  to  half  an  hour  for  the  surplus  coating  to  run 
off;  and  it  is  necessary  that  the  oven  should  be  hot  to  promote  the 
rapid  and  perfect  drainage,  for  if  any  part  of  the  coating  is  too 
thick  it  will  not  be  oxidized  as  soon  as  the  rest  and  will  make  a 
soft  and  imperfect  spot  in  the  coating.  This  is  a  matter  of  the 
utmost  importance;  and  it  is,  therefore,  essential  that  the  oven 
should  be  uniformly  heated  and  particularly  that  there  should  be 
no  leaks  or  crevices  through  which  the  cold  air  from  without  can 
get  in,  for  a  jet  of  this  cold  air  would  infallibly  make  a  bad  spot 
on  the  coating.  The  tendency  of  the  hot  air  to  get  out  and  of 
the  cold  air  to  enter  is  very  strong,  because  at  the  temperature 
of  the  oven,  400°  F.,  the  density  of  the  outer  air  is  twice  that 
of  the  hot  air  in  the  oven.  After  the  coated  object  has  been  in 
the  oven  about  two  hours  it  is  done,  and  when  removed  and  cooled 
it  is  ready  to  be  put  in  service.  It  is  not  to  be  forgotten  that  the 
object  of  heating  the  oven  is  to  increase  the  chemical  activity  of 
the  oxygen  and  of  the  oxidizable  material,  and  that  the  same 
results  may  be  reached  by  baking  at  a  lower  temperature  for  a 
longer  time,  or  at  a  higher  temperature  for  a  short  time.  The 
principal  difficulty  is  in  the  matter  of  drainage;  if  the  oven  is  not 
fairly  hot  the  drip  does  not  run  off  properly,  and  if  it  is  very  hot 
it  may  not  be  uniform.  Some  things  can  be  coated  and  the  excess 
wiped  off;  wire,  for  example,  after  dipping  can  be  drawn  through 
a  hole  in  scraper  which  will  allow  only  the  exact  amount  needed 
to  go  on  into  the  oven,  and  I  have  in  this  way  baked  a  good  coating 
on  wire  in  twelve  or  fifteen  minutes  at  a  temperature  of  500°  to 
600°  F.  This  is  rather  delicate  work,  because  it  is  necessary 
to  know  exactly  the  temperature,  and  from  previous  experiments 
exactly  the  time  required,  and  remove  the  wire  at  just  the  right 


WATER-PIPE  COATING.  281 

time,  or  it  will  be  overbaked  and  brittle.    It  could  be  easily  done 
on  a  large  scale  automatically. 

The  Dipping-tank. — The  dipping-tank  may  be  a  horizontal 
trough  or  a  vertical  tank  of  cylindrical,  oval,  or  other  convenient 
horizontal  section;  for  coatir.g  straight  pipes  nothing  is  better  than 
a  vertical  cylindrical  tank,  about  a  foot  larger  in  diameter  than 
the  pipe.  If  the  pipe  is  not  straight  the  tank  may  be  made  ova1, 
or  the  lower  part  cylindrical  and  the  upper  part  oval.  Such  a 
tank  will  naturally  be  made  of  riveted  steel  and  must  be  heated 
by  an  external  flue.  It  is  impracticable  to  heat  such  a  tank  by 
a  steam-jacket  or  to  heat  any  tank  with  a  steam-coil;  for  by  the 
continual  heating  and  cooling,  rivets  will  get  loose  and  leaky,  and 
the  joints  of  a  steam-coil,  though  when  new  they  may  be  tight  at 
1000  Ibs.  pressure,  will  in  time  leak  a  little;  and  a  very  slight 
leakage  of  steam  into  the  compound  will  in  time  destroy  it.  The 
tank  should  never  be  exposed  directly  to  the  fire,  but  it  may  be 
conveniently  heated  by  a  flue  which  intervenes  between  the  fur- 
nace and  the  chimney.  The  whole  should  be  well  insulated  to 
prevent  radiation,  and  it  is  to  be  remembered  that  neither  in  the 
dipping-tank  nor  the  oven  is  there  any  evaporation  of  liquid,  hence 
very  little  fuel  will  be  needed  if  proper  insulation  is  secured. 

Treatment  of  the  Compound. — The  heating-flue  should  never 
come  up  as  high  as  the  lowest  level  which  will  ever  be  reached  by 
the  compound  in  the  tank;  if  it  does,  the  part  of  the  shell  of  the 
tank  above  the  level  of  the  liquid  will  be  overheated,  and  as  it  is 
alternately  wet  and  dry  as  the  level  is  disturbed  in  use,  it  will  be 
covered  with  thickened  and  overcooked  compound,  which  will 
from  time  to  true  be  redissolved  in  the  liquid,  which  is  thereby 
made  thick  and  viscid,  far  more  than  would  be  supposed;  for  it 
is  a  peculiarity  of  varnishes  in  general  that  an  overcooked  por- 
tion of  varnish  continually  grows  thicker  until  it  becomes  a  jelly, 
and  what  is  more  remarkable,  it  imparts  this  property  to  fresh  and 
uninjured  varnish  to  which  it  is  added.  In  this  way  it  acts  exactly 
as  though  it  were  a  ferment.  I  do  not  suppose  it  is  a  ferment, 
though  some  enzymotic  ferments  act  under  about  as  unlikely  con- 
ditions; but  the  chemical  character  of  these  charges  is  unknown. 


282  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

So  far  as  I  know,  overcooked  oil  does  not  act  in  this  way,  but 
only  the  compounds  containing  oil  united  with  resinous  matter. 
An  overcooked  varnish  may  be  thinned  with  spirits  of  turpentine, 
and  will  keep  growing  thick,  until  an  incredible  amount  of  tur- 
pentine has  been  added  without  avail;  but  turpentine  is  not  neces- 
sary, for  this  pipe  compound  does  the  same  thing  and  there  is  no 
turpentine  in  it.  It  is  a  strange  thing,  but  it  is  true  nevertheless, 
and  if  the  compound  in  a  tank  gets  overcooked,  all  that  can  be 
done  is  to  throw  it  away  and  clean  the  tank  out  absolutely  clean, 
so  that  not  a  trace  of  the  old  compound  is  left  in  it,  before  refilling 
it.  If  the  compound  is  only  a  little  thickened  it  may  be  thinned 
with  a  properly  made  thinner,  which  is  a  similar  compound  made 
with  a  large  excess  of  oil;  but  this  is  a  makeshift.  The  man  in 
charge  of  the  work  should  be  strongly  impressed  with  the  great 
importance  of  not  spoiling  his  compound  by  overheating  it,  which 
he  is  most  likely  to  do  by  trying  to  heat  it  from  a  cold  condition 
too  quickly.  It  should  be  heated  very  gently;  if  there  is  a  large 
amount,  the  heating  should  be  begun  the  day  before  it  is  to  be 
used.  Of  course,  when  the  work  is  continuous  from  day  to  day 
the  heat  is  never  allowed  to  go  down  altogether.  But  no  amount 
of  care  will  avail  if  the  heating-flue  extends  above  the  level  of  the 
liquid  in  the  tank. 

Horizontal  Tanks. — Instead  of  using  a  vertical  tank,  horizon- 
tal ones  are  in  use  in  some  of  the  navy-yard  plants.  These  are 
more  convenient  for  dipping  objects  of  irregular  section,  or  with 
projecting  parts,  as  such  things,  after  being  heated  in  the  oven, 
may  be  laid  in  the  tank  and  the  hot  compound  poured  with  ladles 
over  the  uncovered  parts.  It  is,  besides,  possible  to  get  along  with 
a  less  amount  of  compound  in  those  tanks;  and  if  made  in  the 
way  I  shall  describe,  one  end  of  the  tank  may  be  heated  (for 
coating  small  articles,  such  as  pipe-fittings)  and  the  rest  of  the 
tank  left  cold.  It  is  not  a  good  plan  to  make  such  a  tank  of  steel 
plate  and  heat  with  a  flue,  unless  it  is  for  larger  work  than  has 
yet  been  done.  It  has  recently  been  proposed  to  coat  bridge  mem- 
bers in  this  way  and  very  likely  a  horizontal  steel  tank  might  then 
be  the  best;  but  for  ordinary  work  a  horizontal  tank  should  be 


WATER-PIPE  COATING.  283 

made  in  cast-iron  sections,  each  section  being  a  short,  wide,  and 
deep  trough  with  open  ends;  the  ends  should  be  flanged,  and  the 
sections  should  then  be  bolted  together  to  make  a  long  trough,, 
the  ultimate  ends  of  which  may  be  closed  with  plates  bolted  on. 
Each  of  these  sections  should  be  cast  with  a  steam-jacketed  double 
bottom,  like  a  soap- kettle;  and  these  should  be  separately  piped, 
each  with  its  own  independent  inlet  and  outlet,  for  steam  at  60 
or  80  Ibs.  pressure.  These  steam-jackets,  being  made  of  cast  iron 
without  rivets,  cannot  leak  into  the  compound,  and  it  is  impossible 
to  overheat  the  latter.  Several  of  the  sectional  tanks  have  beea 
built  and  are  giving  the  greatest  satisfaction.  If  only  one  section 
is  desired,  a  steel-plate  diaphragm  may  be  put  in  to  divide  the 
compound  in  this  section  from  the  rest  of  the  trough;  as  there  is 
no  hydrostatic  pressure  there  is  no  particular  tendency  for  the 
compound  to  leak  by,  and  that  in  the  rest  of  the  tank  remains  un- 
melted.  The  disadvantage  of  this  kind  of  a  tank  is  that  it  exposes 
a  large  surface  to  the  air  and  the  compound  tends  to  oxidize  in 
the  tank;  it  is  not  as  rapidly  worked  nor  as  convenient  as  a  ver- 
tical tank,  especially  for  pipe ;  only  one  piece  can  be  dipped  at  a, 
time,  and  in  coating  small  pipe  it  is  common  to  dip  a  hundred  at 
a  time  in  a  vertical  tank;  and  it  is  more  difficult  to  keep  dirt  out 
of  it.  Everything  which  goes  into  an  oven  has  to  drip,  conse- 
quently most  things  have  to  be  supported  with  their  longer  axis 
vertical.  Pipes  can  be  baked  in  no  other  position,  and  so  nearly 
all  ovens  are  vertical;  if  the  tank  is  also  vertical,  the  top  of  it  may 
be  level  with  the  top  of  the  oven,  which  is  in  many  ways  conven- 
ient. A  pipe-coating  plant  should  be  built  on  a  vertical  plan 
throughout  if  at  all  possible. 

The  Oven. — The  essential  thing  about  the  oven  is  that  it 
should  contain  pure  hot  air.  The  process  is  one  of  oxidation,, 
and  the  carbonic-acid  and  other  gases  from  the  furnace  should 
not  be  allowed  to  enter,  nor  should  the  smoke  and  ashes;  it 
may  be  heated  by  an  external  or  internal  flue  or  flues,  or  the 
air  which  it  contains  may  be  heated  in  an  external  stove  and 
forced  into  the  oven  with  a  blower.  On  very  large  work  the 
latter  would  be  the  best,  as  it  would  insure  steadiness  and  uni- 


284  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

formity  of  heat.  Further,  the  oven  should  be  of  such  a  shape 
that  the  coated  object  can  be  supported  in  it,  either  by  suspen- 
sion or  by  resting  on  a  grating  in  such  a  position  that  it  will 
drain  quickly  and  uniformly;  it  mv.st  be  so  tight  that  drafts  of 
cold  air  cannot  enter;  and  the  bottom  of  the  oven  must  not  be 
heated,  because  the  drip  will  fall  on  it  drop  by  drop,  and  if  it  is 
hot  these  drops  will  char  and  be  destroyed  and  will  fill  the  oven 
with  smoke.  This  drip  must  be  caught  in  a  removable  drip- 
pan,  and  by  it  run  off  into  a  convenient  receptacle  which  can 
from  time  to  time  be  emptied  into  the  tank.  There  must  be  some 
means  provided  for  varying  the  heat  in  the  top  and  bottom  of 
the  oven,  so  that  if  one  part  is  too  hot  the  heat  may  be  partly 
withdrawn  and  diverted  to  another.  This  may  be  effected  by 
having  two  or  three  entirely  separate  heating- flues :  one,  for  exam- 
ple, to  heat  the  lower  part  of  the  oven,  another  for  the  middle 
region,  and  a  third  for  the  upper  portion.  Or  it  is  possible  that 
a  single  flue,  surrounding  the  oven,  with  an  outlet  to  the  chimney 
near  the  bottom  and  several  separately  controlled  inlets  at  differ- 
ent heights  from  the  furnace,  might  be  efficacious.  It  has  also 
been  proposed  to  cause  the  air  to  circulate  vertically  in  the  oven 
by  withdrawing  it  from  the  bottom  and  blowing  it  in  near  the  top 
with  a  blower.  Of  course,  if  the  air  is  heated  with  an  external 
flue  and  blown  in  it  will  be  easy  to  arrange  the  heat  as  we  choose. 
Provision  of  some  sort  should  always  be  made  in  an  oven  of 
more  than  12  ft.  in  height  for  local  heating. 

The  common  and  very  satisfactory  kind  of  oven  for  pipe- 
work consists  of  a  steel  cylinder,  not  less  than  i  ft.  larger  in  diam- 
eter and  2  ft.  greater  in  length  than  the  largest  pipe  which  is 
to  be  put  in  it,  securely  set  up  in  a  vertical  position,  and  sur- 
rounded with  a  1 6-  or  2o-in.  brick  casing,  to  keep  the  heat  in. 
Between  the  steel  shell  and  the  brick  wall  is  a  space  of  6  ins.  to 
i  ft.  in  width  all  around,  as  a  flue  for  the  products  of  combus- 
tion from  a  neighboring  furnace  on  their  way  to  the  chimney. 
This  flue  envelops  the  steel  shell  from  top  to  bottom  (but  does  not 
extend  under  the  bottom  of  the  oven)  and  may  be  divided  by  one 
or  two  horizontal  annular  partitions  into  two  or  three  independent 


WATER-PIPE  COATING.  285 

flues.  The  top  of  the  oven  is  covered  with  a  light  cover,  usually 
made  of  sheet  iron  backed  with  a  layer  or  two  of  asbestos-paper, 
and  then  with  inch-boards;  the  cover  keeps  the  heat  in,  and 
can  be  easily  lifted  off  by  a  couple  of  men  when  it  is  time  to 
remove  or  put  in  pipe.  A  gallery  for  these  men  to  walk  on  is 
provided,  a  couple  of  feet  lower  than  the  top  of  the  oven,  and 
this  may  extend  to  and  around  the  top  of  the  dipping-tank,  if 
the  latter  is  of  the  vertical  type.  If  more  than  one  section  of 
pipe  is  to  be  coated  at  once,  as  many  of  these  ovens  as  are  de- 
sired may  be  built  together  in  the  same  mass  of  brickwork; 
each  steel  shell  may  be  made  large  enough  to  take  in  not  more 
than  two  large  pipe-sections  at  a  time.  If  the  units  are  made 
larger  than  this  trouble  will  be  experienced  on  account  of  the 
escape  of  great  quantities  of  hot  air  whenever  the  oven  is  opened 
to  take  out  or  put  in  a  pipe. 

The  dipping-tank  and  oven  must  be  inclosed  in  a  well-lighted, 
substantial  building  which  can  be  heated  in  winter  to  a  tempera- 
ture of  not  less  than  60°;  for  if  the  pipe  is  taken  out  of  the  dipping- 
tank  into  cold  air  or  into  a  wind  of  even  warm  summer  air  the 
compound  on  it  will  be  chilled  and  will  stop  running  off;  three 
or  four  times  as  much  as  is  proper  will  be  carried  over  into  the 
oven,  and  before  it  gets  off  some  of  it  will  have  begun  to  set 
from  the  heat  and  chemical  action,  and  then  it  never  will  run  off, 
and  the  pipe  will  be  unevenly  coated.  It  is  therefore  impor- 
tant to  have  the  whole  apparatus  inclosed  in  a  building.  And  if 
the  pipe  is  to  be  lowered  down  into  the  oven  from  the  top,  it  is 
clear  that  the  building  must  be  somewhat  more  than  twice  as 
high  as  the  oven,  and  some  kind  of  hoisting  apparatus  must  be 
provided;  an  electric  crane  is  probably  the  best  if  much  work 
is  to  be  done,  but  a  derrick  with  a  swinging-boom  has  been  used, 
also  a  trolley,  and  for  occasional  use  still  simpler  apparatus  has 
been  made  to  answer.  The  height  of  the  building  may  be  some- 
times lessened  by  sinking  the  ovens  and  dipping-tank  below 
the  level  of  the  floor.  If  this  is  done  a  blower,  made  especially  for 
hot  air,  such  as  is  used  instead  of  a  chimney  to  induce  draft, 
may  be  used  to  force  the  hot  flue  gases  from  the  furnace  to  the 


286 


TECHNOLOGY  OF  PAINT  AND   VARNISH. 


Enamelling-plant,  Sabin  Process. 


WATER-PIPE  COATING. 


287 


GROUND 


LINE 


CONCRETE  CONCRETE 

VERTICAL  SECTION 


PLAN 

Enamelling-plant,  Sabin  Process. 


288  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

oven;  in  some  situations  it  is  possible  to  build  on  a  side  hill 
and  excavate  on  one  side.  This  is  an  almost  ideal  state  of  things. 
Ovens  opening  from  the  side,  with  a  door  like  a  closet,  have 
been  built.  They  have  so  far  been  not  very  successful.  The 
trouble  is  that  there  is  leakage  around  the  door,  no  matter  how 
carefully  it  is  made,  and  that  side  of  the  oven  is  cooler  than  the 
others.  An  oven  is  now  in  process  of  construction  on  this  plan, 
but  is  built  with  a  sort  of  vestibule,  so  that  leakage  into  or  out 
of  the  oven  is  into  a  little  room  intermediate  between  the  outer 
air  and  the  oven;  this  ought  to  be  more  successful. 

EnameUing-ovens  have  been  built  which  consisted  simply  of 
brick  rooms  heated  by  iron  pipes  which  passed  through  the 
room  and  radiated  heat  which  was  supplied  by  the  furnace  gases 
passing  through  these  pipes;  this  is  a  very  simple  and  efficient 
form;  if  carefully  made,  it  should  be  susceptible  of  the  most 
exact  adjustment  of  temperature.  This  style  of  oven  has  been 
used  for  such  things  as  bicycle  frames  and  the  like,  never  for 
very  large  work. 

In  any  oven  it  is  important  to  have  thermometers.  Nothing 
is  equal  to  a  good  mercurial  thermometer  within  the  limits  of 
its  range,  and  they  can  now  be  had  with  nitrogen  over  the  mer- 
cury, instead  of  a  mercurial  vacuum,  which  can  be  depended 
on  to  800°  F. 

Thermometric  Readings.  —  Any  mercurial  thermometer  has 
range  enough,  if  constructed  for  the  purpose  with  a  long  stem, 
for  this  varnish  enamel  work.  Two  or  three  tubes  of  common 
steam-pipe  should  penetrate  through  the  brick  wall,  the  flue, 
the  iron  shell,  and  enter  an  inch  or  two  into  the  oven;  thermometers 
attached  to  a  rod  can  be  pushed  in  as  far  as  these  pipes  go,  and 
the  outer  ends  of  the  pipes  plugged  with  a  handful  of  fibrous 
asbestos;  from  time  to  time  a  thermometer  may  be  drawn  out 
and  read.  A  thermometer  may  also  be  lowered  from  the  top 
with  a  wire.  It  must  be  remembered  that  the  temperature  indi- 
cated by  the  thermometer  may  not  be  the  actual  temperature 
of  the  greater  part  of  the  oven;  the  thermometer  may  be  in  an 
under-  or  over-heated  place,  but  since  it  is  always  the  same  place, 


WATER-PIPE   COATING.  289 

it  is  sufficient.  The  operator  finds  that  when  the  thermometer 
gives  certain  readings  the  baking  is  successful,  and  then  he  always 
tries  to  keep  the  temperature  at  these  standards.  The  apparent 
temperatures  of  different  ovens,  doing  practically  the  same  work, 
are  usually  different ;  the  real  average  temperature  must  be  about 
the  same.  When  the  plant  is  properly  constructed  almost  the 
whole  thing  is  a  matter  of  temperature. 


CHAPTER  XVII. 

SHIPS'-BOTTOM  PAINTS. 

THERE  are  several  species  of  aquatic  animals  which  bore 
holes  in  unprotected  submerged  wood,  and  are  particularly  dan- 
gerous to  the  bottoms  of  wooden  ships.  To  protect  ships  from 
these  the  practice  arose  of  covering  the  exterior  of  the  ship  below 
the  water-line  with  sheets  of  copper,  as  a  sort  of  armor-plate 
against  aquatic  enemies.  It  was  found  that  not  only  did  the 
copper  protect  from  the  teredo,  but  that  barnacles  and  other 
organisms  did  not  adhere  to  it,  and  this  was  a  great  advantage, 
because  frequently  these  growths  were  several  inches  in  thickness, 
and  impeded  the  rapid  progress  of  the  ship  through  the  water. 
A  coppered  bottom  is,  in  fact,  very  efficacious  at  first ;  it  does  not 
appear  that  it  is  actively  poisonous  to  barnacles  and  the  like,  but 
that  it  has  a  laminated  structure,  probably  from  having  been 
rolled,  and  under  the  action  of  sea-water  the  exterior  laminae 
scale  off,  and  of  course  any  marine  growth  attached  falls  off  with 
the  scale  of  copper. 

Exfoliation  Said  to  be  Superficial. — It  is  said  that  this  lamina- 
tion is  most  marked  near  the  outside  of  the  copper  sheet,  and 
that  the  middle  part  (in  thickness)  of  the  sheet  is  of  more  homo- 
geneous, unstratified  metal;  so  that  after  a  few  years  the  laminated 
part  wears  off,  and  then  the  copper  ceases  to  exfoliate,  and  the 
barnacles  and  other  things  grow  as  well  on  the  copper  as  they 
would  on  anything  else. 

When  iron  ships  came  into  use  the  danger  from  the  teredo 
disappeared,  but  the  loss  of  speed  consequent  on  fouling  with 
barnacles,  weeds,  etc.,  was  as  serious  as  ever;  and  as  the  speed 
of  steamships  increases  the  objection  to  fouling  is  greater.  Chief 

290 


SHIPS'-BOTTOM  PAINTS.  291 

Constructor  Bowles  is  authority  for  the  statement  "that  while 
the  fouling  of  the  battleship  Indiana  between  her  launching  and 
trial  was  very  slight,  it  was  sufficient  to  make  a  difference  to  the 
builders  of  $100,000  in  the  premium  earned  for  speed.  It  probably 
increased  the  resistance  of  the  ship  about  15  per  cent.  A  ship 
subject  to  ordinary  service,  staying  in  port  about  half  the  time, 
will  foul  so  rapidly  that  in  from  six  to  nine  months  there  will  be 
a  loss  of  speed  of  from  25  to  40  per  cent.;  where  ships  are  running 
rapidly  and  regularly  the  loss  is  less."  (Trans.  Am.  Soc.  C.  E., 
Vol.  XXXVT,  p.  494.)  The  prevention  of  fouling  of  iron  and 
steel  ships  is  therefore  a  matter  of  great  and  practical  importance; 
and  as  this  is  attempted  almost  entirely  by  painting,  it  is  proper 
to  give  the  subject  consideration  here. 

I  say  almost  entirely;  for  if  we  attach  plates  of  copper  to  the 
outside  of  a  steel  ship,  as  soon  as  the  sea- water  gets  in  between 
the  two,  as  it  is  sure  to  do,  galvanic  action  sets  up  and  the  steel 
is  rapidly  corroded. 

Wood  Sheathing. — It  has  been  thought  that  if  there  were  no 
metallic  connection  between  the  steel  and  copper  this  action  could 
not  take  place;  so  in  many  cases  the  outside  of  the  ship  has  been 
sheathed  with  3  or  4  ins.  of  wood,  in  the  form  of  planks  bolted 
on,  and  the  copper  sheathing  attached  to  the  wood.  This  has 
not  been  successful  because  the  wood  becomes  water-soaked,  and 
thus  a  galvanic  couple  is  formed.  It  has  always  seemed  to  me 
that  this  method  might  be  made  far  more  successful  by  kiln- 
drying  the  wood,  then  soaking  it  for  a  day  or  two  in  melted  paraffin, 
until  the  latter  had  penetrated  the  planks  to  the  centre. 
During  this  treatment  they  would  shrink  10  per  cent. ;  then  if  they 
were  applied  and  closely  fitted  on,  and  all  interstices  filled  with 
melted  paraffin  or  some  similar  material,  the  water  never  could 
get  in  to  do  any  damage.  Of  course  it  would  cost  money,  but 
the  relative  cost  would  not  be  so  very  much  more,  and  if  it  were 
efficient,  and  the  other  way  is  not,  it  would  be  the  way  to  do  it. 
There  would  still  be  the  objection  that  copper  sheets^  cease  to 
exfoliate  after  two  or  three  years  and  would  have  to  be  torn  off 
and  replaced;  but  the  planking  would  not  need  renewal.  If  a 


292  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

ship  can  be  kept  really  clean  by  recoppering  every  two  years,  or 
perhaps  three,  without  any  other  trouble,  it  might  be  worth  con- 
sidering. 

Electroplating  the  ship  with  copper  has  been  unsuccessfully 
tried.  Electroplate,  if  of  considerable  thickness,  is  a  spongy 
deposit,  and  does  not  answer. 

Paint,  then,  is  practically  the  universal  means  of  protecting 
ships'  bottoms.  All  sorts  of  nostrums  have  been  tried  for  the 
purpose.  The  vagaries  of  inventors  are  infinite  and  unaccountable, 
but  none  are  quite  so  absurd  as  some  of  the  patented  preparations 
which  have  been — not  designed  (they  couldn't  have  been 
designed) — put  together  to  sell  to  the  seafaring  man.  Here  is  a 
sample : 

A  Sample  Patent. — "I  take  100  Ibs.  of  rosin-oil,  100  Ibs.  of 
black  lead,  50  Ibs.  of  French  chalk,  50  Ibs.  of  white  zinc,  75  Ibs. 
of  oxide  of  iron,  and  25  Ibs.  of  tallow.  These  ingredients  are 
thoroughly  mixed.  I  then  heat  together  125  Ibs.  of  thick  tur- 
pentine, 50  Ibs.  of  linseed-oil,  125  Ibs.  of  common  rosin,  25  Ibs. 
of  Gallipoli  oil,  and  125  Ibs.  of  tallow;  and  when  the  mixture  is 
cold  I  mix  with  it  25  Ibs.  of  shellac  dissolved  in  50  Ibs.  of  alcohol 
or  naphtha.  I  then  add  to  the  mixture  50  Ibs.  of  Venetian  red, 
125  Ibs.  of  zinc  paint,  and  thoroughly  mix  the  ingredients.  I  then 
add  to  the  mixture  50  Ibs.  of  tar-spirit  and  again  thoroughly  stir 
the  mixture.  The  two  compositions  thus  formed  are  then  thor- 
oughly mixed  and  the  paint  is  ready  for  the  market. " 

This  mixture  was  patented  by  an  Englishman,  both  in  Eng- 
land and  America;  and  while  it  is  more  elaborate  than  most  it 
can  hardly  be  said  to  be  more  absurd  or  less  efficacious. 

Practically  there  are  now  in  general  use  three  kinds  of  ships'- 
bottom  paints.  All  require  a  first  coal,  which  is  essentially  the 
same  in  all  cases,  being  a  quick-drying  spirit  varnish.  This  is  said 
to  prevent  rusting,  and  is  called  the  anti-corrosive  coating  as 
distinguished  from  the  second  or  anti-fouling  coating. 

Copper-oxide  Paint. — In  the  first  class  of  these   anti-fouling 

faints  the  pigment  is  oxide  of  copper,  which  is  claimed  to  be 

poisonous.   This  is  mixed  with  a  varnish  similar  to  that  used  with 


SHIPS'-BOTTOM  PAINTS.  295 

the  anti-corrosive  paint,  which  latter  has  commonly  an  oxide  of 
iron  as  its  pigment.  I  am  told  that  6,000,000  Ibs.  of  copper  scale 
(oxide)  are  annually  used  for  this  purpose  in  the  United  States. 
The  efficacy  of  this  class  of  paints  is  a  matter  of  dispute.  I  believe 
that  neither  the  navy  or  any  of  the  more  important  steamship 
lines  use  these  paints,  whose  most  undeniable  merit  is  the 
moderate  price  at  which  they  may  be  sold.  Their  very  great 
sale,  on  the  other  hand,  may  be  taken  as  clear  proof  that  they 
are  not  worthless.  I  have  had  no  personal  experience  with  them, 
my  own  experiments  having  been  along  a  different  line,  as  will 
be  told  later. 

The  Varnish  Used. — The  varnish  used  in  these  paints  con- 
tains little  or  no  oil,  but  is  made  of  a  cheap  grade  of  Kauri  or 
some  similar  resin  dissolved  in  benzole  or  some  solvent  of  which 
benzole  is  a  considerable  ingredient,  some  cheap  grade  of  coal- 
tar  naphtha,  mixed  probably  with  a  little  benzine,  and  sometimes 
with  a  little  wood-alcohol  and  fusel-oil.  As  they  are  used  in  the 
open  air  the  odor  of  these  liquids  is  not  particularly  objectionable; 
and  it  would  make  no  difference  if  it  were,  for  an  oleo-resinous- 
varnish  is  not  good  for  such  service,  and  it  is  necessary  to  use  a 
solvent  which  will  dissolve  a  suitable  resin.  Paints  of  this  sort 
dry  in  an  hour  or  two,  so  that  the  second  coat  may  be  applied 
almost  immediately. 

It  is  not  impossible  that  the  resin  itself  is  repellent  to  the 
organic  growths,  at  least  in  some  degree.  I  know  of  at  least  one 
very  successful  maker  of  this  kind  of  paint  who  believes  that  the 
copper  oxide  he  uses  is  chiefly  valuable  as  a  selling  feature  and 
that  the  varnish,  which  is  of  a  peculiar  kind,  is  what  keeps  the 
barnacles  off.  There  may  be  something  in  this.  I  am  certain 
that  the  common  buffalo- moth  can  be  kept  out  of  rugs  by  var- 
nishing the  floor  on  which  the  rug  is  laid,  two  or  three  times  a 
year  with  a  good  Kauri  varnish;  and  some  other  insects,  equally 
objectionable,  will  not  come  into  a  house,  the  entire  woodwork  of 
which  is  kept  well  varnished.  We  know  that  these  oleo- resinous 
varnishes  continue  to  harden  for  a  year  or  more,  which  shows 
that  some  slow  chemical  action  is  going  on,  and  although  we  can 


294  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

detect  no  odor  it  must  be  that  something  objectionable  to  the  more 
acute  sensations  of  insects  is  being  given  off.  I  have  no  doubt 
about  this,  although  I  do  not  understand  what  takes  place.  But 
if  this  is  so,  it  may  be  possible  that  the  right  kind  of  a  varnish 
may  prevent  the  adhesion  of  marine  growths  to  the  bottom  of  a 
vessel.  It  is  all  a  question  of  evidence,  and  I  am  not  aware  that 
a  sufficient  amount  of  evidence  is  accessible. 

Poisonous  Ingredients. — The  same  kind  of  a  varnish  is  used 
with  the  second  sort  of  paint,  but  the  pigment  is  usually  iron 
oxide  or  something  of  the  kind,  to  which  has  been  added  from  half 
,  a  pound  to  a  pound  per  gallon  of  some  mercury  compound.  Some 
makers  claim  to  use  oxide  of  mercury,  others  chloride;  probably 
it  makes  little  difference,  as  it  is  converted  into  the  extremely 
poisonous  bichloride  of  mercury  (corrosive  sublimate)  by  the 
action  of  sea-water.  This,  of  course,  kills  anything  which  tries 
to  adhere  to  its  surface;  and  as  the  varnish  is  gradually  worn  off 
fresh  supplies  of  poison  are  exposed,  until  the  anti- fouling  coat 
is  practically  gone.  Arsenic  does  not  seem  to  be  efficacious ;  mer- 
cury is  practically  the  only  poison  in  use.  Paints  of  this  sort,  if 
well  made,  are  very  satisfactory;  but  they  are  expensive,  and  of 
course  have  to  be  renewed  frequently.  The  rule  in  the  navy  is 
to  repaint  the  bottoms  of  ships  every  six  months.  The  time  varies 
according  to  the  kind  of  service,  the  temperature  of  the  water,  and 
many  other  things;  the  same  paint  will  seldom  give  similar  results 
twice  on  the  same  boat. 

Copper-soap  Paint. — The  third  kind  of  paint  is  of  an  entirely 
different  nature.  It  is  essentially  a  copper  soap,  made  by  precipi- 
tating a  common  soda  soap  from  solution  by  adding  a  solution  of 
sulphate  of  copper,  making  a  stearate  or  oleate  of  copper;  with 
this  is  probably  mixed  some  tallow  or  other  grease.  The  mixture 
is  made  liquid  by  heat  and  is  applied  in  a  melted  condition  with 
brushes,  exactly  as  melted  wax  was  used  on  ships'  bottoms  two 
thousand  years  ago,  as  described  by  Pliny.  This  paint  is  applied 
in  a  rather  thick  layer,  about  ^  in.  in  thickness,  and  is  slowly 
worn  off  by  the  action  of  the  water  as  the  boat  moves  rapidly 
through  it.  Its  action  is  therefore  similar  to  the  exfoliation  of 


SHIPS'-BOTTOM  PAINTS.  295 

copper,  and  is  quite  effectual.  It  is  claimed  by  those  who  sell  it 
that  the  bottom  of  the  boat  is  by  its  use  rendered  slimy,  and  thus 
the  friction  is  decreased;  but  it  is  to  be  noticed  that  racing  yachts 
use  a  hard  varnish,  which  may  fairly  be  taken  as  a  demonstration 
that  the  soap  paint  has  no  superiority  in  that  respect,  though  it 
certainly  does  seem  to  be  very  smooth. 

In  1900  I  prepared  carefully  thirty  plates  painted  with  various 
anti-fouling  coatings,  which  it  had  been  determined  by  previous 
experiments  to  investigate.  These  consisted  of  (i)  an  oleo-resinous 
varnish,  containing  rather  more  than  30  gals,  of  oil  to  each  100 
Ibs.  of  Kauri  resin;  (2)  a  spirit  varnish  made  by  dissolving  Manila 
resin  in  a  suitable  solvent;  (3)  a  similar  varnish,  made  from  a 
more  easily  dissolved  resin  than  Manila,  but  otherwise  much  like 
it;  (4)  shellac,  in  alcohol;  and  (5)  a  rather  complex  varnish  con- 
taining a  proportion  of  shellac,  and  also  oil.  The  second,  third, 
and  fourth  of  these  were  also  used  with  the  addition  of  various 
fixed  oils :  linseed,  tong,  and  castor.  All  were  made  into  paints  by 
adding  a  neutral  pigment,  unacted  on  by  the  varnish  or  sea- water ; 
and  each  was  tried  with  the  addition  of  a  mercury  compound  and 
also  (separately)  with  arsenic.  Some  of  the  latter  trials  were 
duplicated,  using  in  one  case  powdered  metallic  arsenic  and  in 
the  other  white  arsenious  acid.  Some  of  the  mercury  tests  were 
in  triplicate,  using  i  lb.,  i  lb.,  and  i  Ib.  of  mercury  to  the  gallon 
of  paint.  Besides  these  were  half  a  dozen  special  paints,  one  of 
which  (for  purposes  of  comparison),  was  a  well-known  proprie- 
tary ships '-bottom  paint  of  excellent  quality.  The  result  may  be 
briefly  told.  The  oleo-resinous  varnish  made  a  very  fair  paint, 
but  was  soft  and  would  have  been  easily  scraped  off;  the  Manila 
varnish  was  hard,  and  with  the  addition  of  a  little  oil  was  a  good 
paint;  the  other,  more  soluble  copal,  was  not  as  good  as  Manila; 
the  shellac  went  to  pieces;  so  did  the  special  paints;  but  No.  5, 
which  was  a  mixed  varnish,  gave  the  best  results  of  all,  a  little 
better  than  the  standard  proprietary  paint,  indicating  that  a  little 
shellac  and  a  very  little  wax  are  useful  additions  to  such  a  paint. 
Kauri  was  the  best  resin;  mercury  was  much  better  than  arsenic; 
and  a  considerable  proportion  of  mercury  is  desirable.  The  best 


296  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

paints  were,  unfortunately,  the  most  expensive,  and  none  of  them 
showed  much  durability  after  a  year's  exposure;  some  were  nearly 
destroyed  before  that  time.  No  experiments  in  this  series  were 
made  with  the  copper  soap  or  grease  paints,  nor  with  copper  oxide. 
It  seemed  possible  to  make  a  somewhat  better  mercury  paint  than 
is  now  in  use,  but  not  a  great  deal  better;  and  the  difficulty  of 
carrying  on  these  experiments  is  prodigious. 

In  conclusion  it  may  be  added  that  some  of  the  yachtsmen,  to 
whom  expense  is  not  an  objection,  varnish  the  bottoms  of  their 
vessels,  sometimes  with  spar  varnish  and  sometimes  with  a  spirit 
varnish,  and  while  the  surface  is  tacky  rub  it  over  (with  a  brush) 
with  copper-bronze  powder;  and  this  is  said  to  be  very  excellent- 
Often  the  bronze  powder  is  mixed  with  the  varnish  before  the 
latter  is  applied.  Racing  yachts  usually  receive  nothing  but  var- 
nish, or  a  thin  varnish  paint,  applied  a  day  or  two  before  the 
race.  Probably  no  other  surface  offers  so  little  friction  as  that  of 
a  clear,  well-dried  varnish. 


CHAPTER  XVIII. 

SHIP-  AND  BOAT-PAINTING. 

WITH  a  few  exceptions  the  methods  and  materials  used  in 
house-painting  are  applicable  to  ships  and  boats,  the  most 
remarkable  difference  being  in  painting  the  outside  of  pleasure- 
craft,  which  are  commonly  white.  This  color  gives  a  cool  and 
agreeable  effect;  but  as  these  vessels  spend  much  of  their  time 
in  harbor,  and  as  harbor-waters  are  frequently  covered  with  a 
black,  slimy,  oily  film,  they  quickly  become  foul,  and  are  then 
anything  but  pleasing  to  the  eye.  The  remedy  for  this  state  of 
things  is  one  which,  from  a  painter's  viewpoint,  may  fairly  be 
called  heroic. 

White  Paint  for  Boats. — To  keep  them  white,  they  are  painted 
with  white  lead,  mixed  not  with  oil  but  with  spirit  of  turpentine. 
Paste  white  lead,  containing  10  per  cent,  of  oil,  is  mixed  up  with 
turpentine,  and  after  standing  overnight  to  settle,  the  turpentine 
is  poured  off;  this  removes  about  half  of  the  oil.  The  residue 
is  then  mixed  with  fresh  turpentine,  and  the  boat  painted  with 
it.  In  this  way  is  obtained  a  coating  of  unparalleled  whiteness, 
for  the  yellowish  tint  of  ordinary  white  paint  is  due  to  the  oil  it 
contains;  but  paint  made  in  this  way  is  necessarily  lacking  in 
binding  material.  It  therefore  washes  off  easily,  and  thus  exposes 
a  fresh  surface.  As  it  dries  with  great  rapidity,  owing  to  the  small 
amount  of  oil  it  contains,  and  the  excessive  thinness  of  film  which 
this  oil  has,  it  is  possible  to  apply  many  coats  in  rapid  succession, 
thus  building  up  a  thick  coat  of  paint;  and  as  there  is  nothing 
about  it  which  has  a  natural  affinity  for  water  it  does  not  become 
water- soaked  and  all  come  off  at  once  from  the  surface  to  which 
it  was  applied,  but  gradually  wastes  away  from  the  outside,  or 

297 


298  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

if  necessary,  may  be  cleaned  off  with  scrubbing-brushes,  thus 
always  presenting  a  white  surface  of  great  purity.  This,  of  course, 
means  frequent  repainting  and  a  use  of  material  which  would  in 
other  cases  be  considered  wasteful;  but  in  no  other  way  can  the 
results  be  obtained. 

On  deck  the  conditions  are  very  different.  The  deck-houses 
are  sometimes  painted,  and  this  should  be  done  with  enamel 
paints,  made  with  the  most  durable  and  elastic  varnishes,  say 
25  to  30  gals,  of  oil  to  100  Ibs.  of  (unmelted)  resin;  the  interior 
of  the  cabins  and  other  rooms  with  a  somewhat  harder  and 
quicker- dry  ing  enamel. 

Spar  Varnish. — Some  of  the  exterior  woodwork,  frequently 
a  large  part  of  it,  is  left  unpainted  and  is  protected  by  "spar" 
varnish;  this  varnished  but  unpainted  wood  is  called,  on  ship- 
board, "bright  work."  The  masts  are  sometimes,  but  not  com- 
monly, painted,  and  the  spars  are  left  "bright."  Spar  varnish 
is  used  on  these,  and  this  is  the  origin  of  the  name.  Spar  var- 
nish is  a  very  durable  and  elastic  varnish,  pale  in  color  though 
not  excessively  so,  for  a  yellow  varnish  looks  well  on  spruce, 
and  dark  varnishes  are  much  better  than  pale  ones  on  mahogany 
and  such  woods,  and  should  contain  not  less  than  25  gals,  of  oil 
to  100  Ibs.  of  resin.  It  is  in  fact  very  much  such  a  varnish 
as  is  used  for  a  finishing  coat  on  carriages,  except  that  it  must 
dry  more  quickly.  If  a  boat  could  be  built  in  a  shop  and  var- 
nished in  a  room  free  from  dust,  carriage-finishing  varnish  would 
be  better  than  spar;  but  in  practice  the  quicker-drying  varnish  is 
the  better.  It  is  frequently  a  more  fluid,  or  thinner,  varnish  than 
such  as  are  made  for  shop  work.  This  tends  to  make  a  thinner 
film,  which  is  less  durable,  but  is  quicker  to  dry;  and  as  most 
spar  varnish  is  used  on  repair  work,  it  is  absolutely  necessary 
that  it  should  dry  quickly.  It  is  even  the  practice  in  some  of  the 
best  yards  to  thin  it  with  spirit  of  turpentine  for  very  hurried 
work;  and  this  is  better  than  adding  drier,  though,  of  course,  it 
makes  a  still  thinner  and  more  perishable  coating  than  the  regu- 
lar spar.  Sometimes  spar  varnish  is  applied  to  the  unfilled  wood, 
and  repeated  coats  used  until  a  sufficient  body  has  been  built 


SHIP-  AND  BOAT-PAINTING.  299 

up,  and  this  is  the  best  practice;  in  this  way  the  wood  is  pro- 
tected by  a  homogeneous  coating  which  no  severity  of  exposure 
can  cause  to  separate^  but  often  a  cheaper  varnish  is  used  for 
the  under-coat  work.  This  should  be  similar  in  its  nature  to  spar; 
rubbing-varnish  is  not  fit  for  this,  and  worst  of  all  is  shellac. 
The  latter  is  often  used  because  of  its  excessive  rapidity  of  dry- 
ing; but  as  has  been  already  stated,  this  rapidity  is  partly  only 
apparent;  and  at  any  rate  shellac  is  not  a  varnish  which  ought 
to  be  exposed  to  the  hot  sun,  nor  to  sea- water,  and  not  infre- 
quently causes  blisters  under  the  spar  varnish  which  is  subse- 
quently applied. 

Shellac. — There  is  a  legitimate  use  for  shellac  on  board  ship. 
Some  of  the  decks,  not  exposed  to  the  weather,  but  those  which 
serve  as  floors,  must  be  scrubbed  clean  daily;  and  as  it  is  mani- 
festly impossible  to  use  a  slow- dry  ing  varnish  on  these,  the  best 
thing  is  a  thin  shellac,  one  coat  of  which  will  dry  almost  imme- 
diately, and  will  answer,  for  a  day  or  two,  to  prevent  grease  and 
dirt  from  penetrating  the  wood.  This  is  especially  the  case  on 
men-of-war,  where  large  numbers  of  men  are  crowded  into  con- 
fined spaces,  and  the  sanitary  value  of  varnish  is  of  the  utmost 
account;  not  only  does  it  keep  out  the  dirt,  but  the  strong  alcohol 
and  the  resin  both  act  as  germicides.  But  nothing  is  more  repre- 
hensible than  the  practice  which  some  captains  have  of  ordering 
all  the  bright  work  varnished,  over  and  over  again,  with  shellac. 
It  is  not  uncommon  to  see  naval  vessels  come  in  from  a  cruise 
with  the  bright  work  so  bedaubed  and  plastered  with  shellac 
that  it  was  enough  to  discourage  the  constructor  and  the  master 
painter  from  ever  trying  to  make  a  ship  look  well.  Spar  var- 
nish, and  that  of  the  best  quality,  and  not  too  much  of  it,  is  the 
only  thing  which  should  ever  be  used  on  bright  work;  it  may 
be  cleaned  and  repolished  as  often  as  necessary.  It  is  good  prac- 
tice to  use  spar  also  when  it  is  necessary  to  thin  enamel  paints, 
rather  than  to  use  turpentine  or  oil;  nothing  is  better  for  this 
purpose  on  land  as  well  as  at  sea. 

Ships  are  often  repainted  too  much;  a  naval  constructor 
told  the  writer  that  he  had  removed  layers  of  paint  which  con- 


300  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

tained,  when  viewed  with  a  microscope,  over  a  hundred  laminae. 
It  seems  as  though  the  officers  who  were  responsible  for  this 
ought  to  be  taught  a  little  common  sense.  Yachts  and  other 
pleasure-boats  are  looked  after  with  more  intelligence  in  this 
respect,  and  are  usually  in  admirable  condition. 

A  white  interior  enamel  is  often  made  for  some  of  the  cabins 
of  ships,  especially  in  the  navy,  by  mixing  the  pigment  with 
damar  varnish.  This  probably  makes  the  whitest  enamel;  but 
it  lacks '  durability,  and  especially  very  quickly  loses  its  gloss. 
On  vessels  of  any  value  it  is  advisable  to  use  a  better  article, 
for  a  good  oleo-resinous  enamel,  which  is  white  enough  for  the 
finest  house,  is  certainly  white  enough  for  a  cabin;  and  it  has 
durability.  Damar  dries  more  quickly,  but  never  has  as  good 
a  surface,  and  it  is  certainly  better  to  use  a  more  permanent 
coating. 


E 


u 


I! 


CHAPTER  XIX. 

CARRIAGE-PAINTING. 

To  treat  fully  of  the  painting  of  carriages  and  coaches  would 
require  a  volume,  and  volumes  have  been  written  about  it;  but 
the  casual  inquirer  into  the  art  may  be  satisfied  with  an « outline 
of  the  methods  and  the  principles  involved.  It  has  always  been 
near  the  border  between  artistic  and  industrial  painting,  and 
its  practitioners  have  held  a  high  rank.  Carriages  must  be 
pleasing  to  the  eye;  but  still  more  they  must  be  strong  and  dur- 
able, retaining  not  only  their  form  and  strength,  but,  if  possible, 
their  finish  after  exposure  to  the  inclemencies  of  the  sun,  wind, 
mud,  and  rain. 

Severe  Exposure  of  Varnish  on  Carriages. — Pictures  are  pro- 
tected by  frames,  hung  on  shaded  walls,  untouched  save  to  remove 
carefully  the  dust  which  settles  on  them ;  furniture  is  indeed  used, 
often  carelessly,  sometimes,  though  not  usually,  exposed  to  the 
sun,  but  at  any  rate  it  is  protected  from  the  snow  and  rain ;  but 
carriages  are  drawn  by  horses,  or  propelled  by  engines,  rapidly 
through  grinding  sand,  dust,  mud,  and  exposed  to  injury  from 
branches  of  trees  and  accidents  of  every  sort,  yet  the  surface 
must  be  polished  and  lustrous,  and  the  moisture  must  be  kept 
out  of  the  wood,  or  it  will  fall  in  pieces.  The  deacon's  one-hoss 
shay  was,  we  may  be  sure,  painted  and  varnished  with  a  knowl- 
edge and  skill  which  need  not  have  shamed  its  historian;  else 
there  would  have  been  no  tale  to  tell. 

It  is  a  general  belief  that  carriages  are  painted  in  a  less  durable 
manner  than  was  formerly  the  practice;  and  this  is  in  some 
instances  probably  true.  It  must  be  remembered,  however,  that 
where  one  carriage  has  lasted  for  a  generation  thousands  have 

301 


302  TECHNOLOGY  OF  PAINT  AND    VARNISH 

perished,  leaving  no  sign,  in  a  few  years;  and  probably  some  of 
our  posterity  will  point  to  a  few  long-surviving  coaches  of  our  own 
time  as  we  do  to  the  relics  which  have  come  down  to  us.  It  must 
be  that  there  have  always  been,  as  there  are  now,  good  finishers 
and  poor.  The  latter  are  soon  forgotten  if  they  belong  to  a  former 
generation,  but  if  they  are  our  own  contemporaries  we  not  only 
remember  them  but  unjustly  judge  their  better  fellow  workmen 
from  their  work.  This  is  indeed  a  general  law.  It  applies  not 
only  to  carriage-painters  but  to  varnish-makers  as  well;  and  there 
will  always  be  those  who  exalt  the  past  at  the  expense  of  the 
present,  and  discredit  the  skilful  workman  because  poor  work  is 
common.  It  has  always  been  common,  and  it  always  will  be. 

Good  Work  is  Slow. — It  is  said  in  the  twenty- eighth  chapter 
of  the  book  of  the  prophet  Isaiah  that  "he  that  believeth  shall 
not  haste";  and  this  may  well  be  taken  for  a  motto,  not  by  car- 
riage-painters alone,  but  by  all  who  have  to  do  with  varnish, 
whether  as  makers  or  users,  and  perhaps  by  some  other  people. 
Good  varnish  is  slow  to  dry,  so  is  good  paint;  a  job  which  must 
be  hurried  will  lack  in  durability,  but  a  job  which  takes  a  long 
time  is  costly. 

It  is  in  general  true  that  it  is  essential  to  have  a  suitable  founda- 
tion on  which  to  apply  a  finish,  whether  for  beauty  or  utility. 
Xenophon,  who  wrote,  four  hundred  years  before  the  Christian 
era,  the  oldest  treatise  on  horsemanship  with  which  we  are 
acquainted,  says  that  "just  as  a  house  would  be  good  for  nothing 
if  it  were  very  handsome  above  but  lacked  the  proper  foundations, 
so  too  a  war-horse,  even  if  all  his  other  points  were  fine,  would  yet 
be  good  for  nothing  if  he  had  bad  feet,  for  he  could  not  use  a 
single  one  of  his  fine  points."  It  is  exactly  so  with  painting; 
if  the  foundation  be  poor  the  subsequent  work  and  material  are 
thrown  away.  The  basic  material  is  wood;  this  must  be  properly 
treated  to  make  a  suitable  foundation.  In  the  first  place  it 
must  be  dry;  not  merely  kiln-dried,  but  previously  well- seasoned; 
but  this  is  a  matter  which  belongs  to  the  art  of  the  wood- worker. 
It  must  be  so  treated  as  to  be  damp-proof,  and  this  involves 
filling  the  pores  of  the  wood  on  both  sides  and  on  exposed  edges; 


CARRIAGE-PAINTING.  3°3 

not  a  place  may  be  omitted.  This  is  equally  true  of  furniture, 
and  in  fact  the  finishing  of  the  latter  is  based  on  the  practice 
of  carriage-painters. 

Filling. — The  pores  of  the  wood,  then,  are  to  be  filled;  the 
first  coat  is  usually  linseed-oil,  to  which  a  little  white  lead  has 
been  added,  just  enough  to  color  the  oil.  Some  painters  use 
varnish  for  the  priming  coat,  but  this  is  because  they  are  in 
haste,  and  they  use  a  quick- dry  ing  varnish,  which  is  not  as  good 
as  oil.  In  place  of  white  lead  some  use  finely  ground  silica,  and 
some  use  yellow  ochre,  and  many  a  mixture  of  these;  but  it  is 
of  little  consequence  in  the  priming  coat,  for  this  is  chiefly  oil, 
and  the  oil  is  really  absorbed  by  the  wood.  The  real  surfacing 
now  begins;  and  many  men  use  many  things.  The  object  all 
aim  at  is  to  get  a  hard,  smooth,  level  surface;  on  this  the  paint 
is  applied,  and  then  the  varnish.  If  the  foundation  is  too  elastic 
it  will  not  hold  the  surface  in  place,  and  the  latter  will  crack,  even 
though  of  tough  and  elastic  material.  These  "elastic  under-coat 
cracks"  are  sometimes  very  puzzling.  The  writer  has  seen  them 
on  the  surface  of  a  highly  elastic  varnish  which  had  been  applied, 
four  coats  in  thickness,  on  a  steel  surface,  as  a  protective  material; 
the  hot  sun  hardened  the  outside  pellicle,  and  when  it  suddenly 
cooled — and  all  such  exterior  work  is  subject  to  frequent  and 
considerable  changes  of  heat — this  surface  cracked,  because  the 
under-coat  was  so  elastic  that  it  practically  gave  it  no  support. 
Such  cracks  are  purely  superficial,  and  are  not  likely  to  affect  the 
protective  action,  but  they  ruin  the  beauty  of  the  finished  surface. 
Elastic  under-coat  cracks,  then,  must  be  prevented  by  making 
the  foundation  hard  and  firm,  and  gradually  working  up,  by  the 
progressive  use  of  more  and  more  elastic  coatings,  to  the  finishing 
varnish,  which  is  as  elastic  as  is  compatible  with  a  sufficient  degree 
of  lustre. 

White  Lead  as  a  Filler. — At  this  stage  the  chief  differences  in 
treatment  are  in  the  use  of  white  lead  or  of  a  filler  composed  of 
silex  or  silicates.  The  older  practice  is  to  use  white  lead,  and 
this  is  susceptible  of  variations.  The  first  method  of  using  lead 
consists  in  painting  the  surface  with  a  white- lead  paint.  This 


304  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

probably  was  originally  white  lead  in  pure  linseed-oil,  but  at  pres- 
€nt  it  is  made  by  thinning  paste  white  lead  (which  is  called  by 
painters  "keg  lead")  with  half  oil  and  half  turpentine;  the  pro- 
portion of  turpentine  is  increased  often  to  five-eighths  and  some- 
times to  three-fourths;  the  greater  the  hurry  the  more  turpentine 
is  used;  five-eighths  turpentine  is  very  common.  This  is  well 
brushed  out  so  as  to  make  as  smooth  a  coat  as  possible.  It  is 
followed  by  another  coat  of  lead  which  is  prepared  by  thinning 
paste  or  "keg"  lead  with  spirit  of  turpentine;  sometimes  a  little 
oil  is  added,  not  usually  as  much  as  5  per  cent,  by  measure. 
Paint  made  in  this  way  will  have  a  lustreless  surface,  called  "flat" 
or  "dead."  Commonly  a  very  little  lampblack  is  added  to  the 
lead  in  both  these  coats,  enough  to  produce  a  lead  or  slate  color; 
and  to  hurry  the  work  about  2  per  cent,  of  japan  is  also  used. 
The  last  coat  should  be  applied  with  great  care,  to  produce  as 
smooth  a  surface  as  possible. 

Rub-lead. — Instead  of  these  two  coats  it  is  also  a  practice  to 
use  what  painters  call  "rub- lead."  This  is  white  lead  mixed  with 
lampblack  to  a  slate  color  and  thinned  with  oil  and  japan.  A  con- 
siderable amount  of  the  latter  is  used,  often  20  or  25  per  cent. 
This  by  good  rights  ought  to  be  ground  through  a  mill.  It  may 
be  remarked  that  the  lampblack  is  thought  to  add  to  the  smooth- 
ness and  flowing  quality  of  the  lead.  This  is  made  of  such  a  con- 
sistency that  it  may  be  brushed  on  with  a  stiff  bristle  brush;  and 
when  it  has  been  on  long  enough  to  set  well  and  be  decidedly  stiff 
the  lead  is  rubbed  well  into  the  pores  of  the  wood;  this  is  best 
done  with  the  palm  of  the  hand.  In  this  way  a  very  fine,  dense 
surface  is  obtained,  and  after  hardening  two  or  three  days  it  is 
ready  to  be  sandpapered. 

Knifing-lead. — More  rapid  work  still  is  done  by  mixing  lead 
to  a  putty  and  applying  it  with  a  putty-knife.  For  this  purpose 
paste  lead  is  mixed  with  about  an  equal  weight  or  twice  its  weight 
of  dry  white  lead  (the  larger  the  proportion  of  the  latter  the  quicker 
it  is  to  work,  because  the  oil  slows  it),  and  with  a  mixture  of  equal 
parts  of  rubbing- varnish  and  japan;  usually  a  little  spirit  of  tur- 
pentine is  added.  In  fact,  painters  of  all  sorts  usually  add  a 


CARRIAGE-PAINTING.  3°5 

little  turpentine  to  everything,  without  much  thought  of  the  con- 
sequences. It  promotes  the  union  of  the  different  parts  of  a  mix- 
ture, as  it  is  a  powerful  solvent,  and  adds  to  the  fluidity  of  the 
whole.  This  lead  compound  is,  for  very  rapid  work,  colored  to 
suit  the  paint  which  is  to  be  used  over  it;  otherwise  it  is  tinted 
with  lampblack.  It  is  either  put  on  with  a  putty-knife  or  is 
thinned  with  turpentine  to  a  very  heavy  paint  and  applied  with  a 
brush,  after  which,  as  soon  as  it  sets,  it  is  worked  into  the  wood 
with  the  flat  blade  of  the  knife,  and  always  the  surplus  is  carefully 
removed.  Rub-lead  is  almost  universally  used  on  wheels  and 
running-gear,  and  frequently  on  bodies;  but  knifing- lead  is  re- 
stricted to  bodies,  the  process  being  adapted  to  flat  surfaces. 

These  are  the  various  ways  in  which  lead  is  used  as  a  filler.  In 
all  cases  after  it  is  thoroughly  hard  it  is  sandpapered  to  get  a  very 
smooth  surface.  If  lead  is  not  used  a  wood-filler  is  applied.  This 
is  of  course  a  paste-filler,  having  a  body  of  powdered  quartz  or 
some  equivalent,  often  containing  some  white  lead ;  and  the  liquid 
in  which  it  is  ground  is  a  varnish.  This  is  well  rubbed  into  the 
wood  with  a  stiff  brush,  and  when  dry  and  hard  is  sandpapered. 
Two  or  more  coats  are  often  applied. 

Putty. — It  is  the  practice  of  house- painters  to  putty  holes  and 
crevices  immediately  after  priming;  but  carriage- painters  usually 
wait  until  the  filler  is  all  in.  The  operation  is  the  same,  except 
that  as  the  work  is  to  receive  one  or  more  additional  surfacing 
coats  and  is  then  to  be  painted,  it  is  not  essential  to  a  fine  finish 
that  so  much  care  be  taken  not  to  scratch  the  surface,  and  steel 
putty- knives  are  used.  If  there  is  a  crack  where  there  is  a  possi- 
bility of  flexibility  between  two  adjacent  pieces  of  wood  it  is  bad 
practice  to  putty  it,  as  the  putty  will  in  time  work  loose  and  come 
out.  Putty,  on  a  carriage,  is  for  nail-holes  and  the  like.  White- 
lead  putty  is  universally  used,  usually  mixed  with  some  japan  to 
make  it  harden  very  rapidly.  Of  course  it  is  more  durable  if 
mixed  only  with  oil,  or  perhaps  finishing-varnish;  but  tough  putty 
cannot  be  sandpapered. 

We  have  now  got  the  woodwork  primed,  filled  (either  with  lead 
or  prepared  filler),  and  puttied.  The  next  thing  is  sandpapering. 


306  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

In  fact  the  first  thing  is  too,  for  before  the  priming  is  applied  the 
painter  should  see  that  the  surface  is  as  level  and  true  as  possible, 
and  if  he  cannot  make  the  wood- worker  turn  it  over  to  him  in 
that  condition  he  must  do  it  himself,  for  that  is  the  time  when  it 
ought  to  be  done  and  can  be  most  easily.  Usually  each  coat  from 
the  priming  up  is  sandpapered  a  little;  but  at  this  point,  after  the 
putty  has  been  applied,  the  surface  must  be  made  as  good  as 
possible,  and  all  dust  be  thoroughly  removed. 

Rough-stuff. — The  next  coat  is  rough- stuff.  The  makers  of 
carriage-paints  prepare  better  rough-stuff  than  the  amateur  ever 
makes;  but  in  general  it  may  be  said  that  it  is  essentially  com- 
posed of  a  silicious  filler — not  quartz,  but  some  mineral  silicate, 
ground  to  a  moderate  degree  of  fineness,  mixed  with  some  white 
lead;  from  a  third  to  a  quarter  the  weight  of  pigment  may  be 
lead,  but  as  lead  is  twice  as  heavy  as  the  silicate,  the  latter  will 
amount  to  five-sixths  or  seven-eighths  the  bulk  of  the  whole. 
Ochre  is  regarded  by  some  as  a  valuable  ingredient.  The  liquid 
is  essentially  a  rubbing-varnish;  the  carriage- painter  who  mixes 
his  own  adds  japan,  but  the  paint  manufacturer  (who  in  this  case 
is  also  a  varnish-maker)  makes  a  special  varnish  which  possesses 
just  the  right  qualities  for  the  purpose  without  the  addition  of  a 
needless  amount  of  injurious  driers.  The  thing  aimed  at  is  to 
make  a  sort  of  paint  which  will  dry  rapidly  to  a  very  hard  surface, 
capable  of  being  ground  down  to  a  smooth,  glassy  finish,  and  at 
the  same  time  have  about  the  same  rate  of  expansion  and  con- 
traction as  the  foundation  on  which  it  rests,  so  that  it  will  not 
crack  and  come  off.  This  is  no  simple  thing  to  accomplish;  and 
it  is  in  general  safer  to  buy  of  a  maker  who  purchases  his  filler  in 
lots  of  one  to  ten  car-loads,  and  always  uses  the  same  materials, 
than  to  try  to  use  those  things  which  are  bought  in  small  quanti- 
ties and  from  miscellaneous  sources. 

It  is  applied  with  the  brush,  and  as  it  is  quick  to  set  it  must 
be  put  on  rapidly  and  smoothly  with  a  soft  brush  and  by  a  skil- 
ful hand.  One  coat  a  day  can  be  put  on;  three  to  five  are  needed, 
and  often  the  latter  number  is  doubled.  If  the  material  is  right 
it  is  not  necessary  to  sandpaper  or  give  similar  treatment  between 


CARRIAGE-PAINTING.  307 

coats  in  order  to  secure  adhesion,  but  a  substantial  body  may  be 
rapidly  built  up. 

Guide-coat. — It  is  usual  to  color  the  last  coat  with  ochre  or 
white  lead.  This  is  called  a  guide-coat,  as  it  serves  as  a  guide  to 
uniform  rubbing  of  the  surface.  After  a  sufficient  amount  has 
been  laid  on  the  whole  should  be  allowed  two  or  more  days  to 
harden.  It  ought  to  be  as  hard  as  it  will  become,  and  time  is  well 
spent  waiting  for  it  to  dry. 

Pumicing. — This  is  not  sandpapered,  but  is  brought  to  a  sur- 
face with  pumice  and  water;  and  in  this  case  the  pumice  is  not 
powdered,  but  blocks  of  natural  pumice-stone,  which  is  a  sort  of 
porous  lava,  are  used.  These  are  sawn  to  the  desired  shape,  ground 
down  on  a  flat  surface,  and  they  are  ready  for  use.  The  lightest 
and  most  open  pieces  cut  most  rapidly;  the  more  dense  are  used 
for  finishing.  The  rubbing  is  not  done  with  circular  or  irregular 
motions,  but  back  and  forth  in  the  same  direction.  The  surface 
is  kept  well  wet  with  pure  water,  but  not  flooded;  but  it  should 
be  frequently  washed  off  and  examined.  It  is  sponged  off  with  a 
clean  sponge,  and  wiped  dry  with  a  clean  piece  of  chamois  leather. 
This  operation  is  to  be  learned  by  experience  and  observation, 
not  from  books.  It  is  one  which  requires  patience  and  skill,  and 
produces  the  surface  on  which  the  color  and  varnish  are  to  be 
exhibited. 

Color. — The  next  step  is  the  application  of  the  color.  Paint 
for  carriages  is  made  of  the  necessary  pigments,  ground  to  the 
last  degree  of  fineness.  They  ought  to  be  ground  as  fine  as  artists' 
tube-colors;  but  instead  of  being  ground  in  oil  they  are  ground  in 
"grinding- japan,"  a  sort  of  varnish,  loaded  nearly  to  the  point  of 
saturation  with  lead  and  manganese  driers.  Not  all  colors  can 
be  ground  in  the  same  medium,  or  they  will  gelatinize  and  spoil. 
Such  must  have  a  special  varnish  or  japan,  the  nature  of  which 
must  be  learned  by  experiment.  These  "coach- colors"  are 
sold  in  air-tight  tin  cans,  well  filled,  and  the  best  of  them  will 
not  keep  forever.  They  should  be  purchased  from  fresh  stock 
as  they  are  needed.  Varnishes  improve  with  age,  but  no  paint 
does,  and  coach-colors  are,  though  perhaps  not  as  bad  as  var- 


308  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

nish- enamel  paints,  worse  than  those  ground  in  oil.  Coach- 
colors  are  sold  in  what  is  practically  a  paste  form,  and  are  to 
be  thinned  with  oil  and  turpentine.  Some  use  varnish  instead  of 
oil,  but  the  latter  is  generally  advised.  They  are  put  on  in  thin 
coats  and  dry  rapidly. 

Rubbing-varnish. — Over  this  is  applied  rubbing-varnish  in 
full,  heavy  coats.  These  do  not  depend  entirely  on  oxidation  for 
hardness,  for  rubbing- varnishes  contain  only  from  6  to  12  gals. 
of  oil  to  100  Ibs.  of  resin,  and  the  large  proportion  of  the  latter 
helps  materially  to  give  them  hardness.  They  should,  however, 
be  allowed  ample  time  to  dry.  They  are  called  rubbing-var- 
nishes because  they  are  hard  enough  to  bear  grinding  down  to  a 
smooth,  even  surface  with  pumice  and  water;  but  in  this  case 
the  blocks  of  stone  are  not  used.  The  pumice  is  powdered,  and 
is  applied  with  a  piece  of  thick  felt,  well  wet  with  clean  water. 
Several  coats  of  rubbing- varnish  are  applied;  not  less  than  three, 
often  more.  Each  coat  is  rubbed;  the  first  lightly,  the  others  more 
thoroughly.  Before  rubbing  the  surface  is  wet  with  clean  water; 
then  the  wet  pad  of  felt  is  touched  to  the  powdered  pumice  and 
the  rubbing  begins.  This  is  an  art  and  must  be  learned;  but 
the  observer  will  notice  that  the  expert  uses  steady  strokes,  all 
in  one  direction;  at  first  rubbing  lightly,  aftirward  with  more 
force.  The  edges  and  mouldings  are  first  treated,  and  the  work- 
man finishes  up  a  panel  in  the  middle.  It  is  easier  to  cross-rub 
the  ends  of  panels ;  but  this  is  not  regarded  as  good  form  by 
many  of  the  professionals.  When  the  surface  has  been  rubbed 
it  is  well  washed,  and  the  utmost  care  is  required  to  have  all 
the  utensils  for  this  service  clean. 

Cleanliness. — An  entire  extra  set  of  sponges  and  chamois 
leather  is  kept  for  finishing  up  the  washing,  so  that  the  surface 
at  last  may  be  as  clean  as  possible.  It  goes  without  saying  that 
all  this  work  of  varnishing  and  cleaning  must  be  done  in  a  room 
kept  clean  and  free  from  dust.  A  varnishing- room  should  not 
contain  shelves  or  anything  to  hold  dust ;  it  must  be  free"  from 
draft,  and  should  be  entered  from  a  vestibule  which  has  a  second 
door  opening  into  some  other  room;  and  the  floor  should  be 


W 


B    _ 

r  2 


CARRIAGE-PAINTING.  309 

higher  than  that  of  the  adjacent  room,  so  that  there  will  be  a 
step  up,  which  helps  to  keep  out  the  dust  which  naturally  lies 
on  the  floor.  Nine-tenths  of  the  trouble  which  varnish-users 
encounter  comes  from  dirty  and  badly  contrived  rooms.  Every 
varnish-maker  is  a  victim  of  innumerable  instances  of  this.  The 
fault  of  the  location  is  attributed  to  the  varnish,  and  the  user  is 
intolerant  of  criticism.  It  is  seldom  of  any  use  to  tell  a  man  that 
his  trouble  is  due  to  his  own  deficiencies,  whether  personal  or 
of  his  surroundings.  He  wants  something  which  will  compensate 
for  those  things ;  he  doesn't  get  it. 

Finishing-varnish. — The  finishing-varnish,  which  contains 
about  25  gals,  of  oil  to  100  Ibs.  of  the  best  hard  varnish- resins, 
and  is  of  all  varnishes  the  most  exacting  and  the  most  difficult  to 
make,  is  in  this  country  often  called  "wearing-body"  varnish. 
It  is  at  once  brilliant,  hard,  elastic,  and  durable.  This  is  the  kind 
of  a  varnish  which  the  great  painters  of  the  middle  ages  were 
trying  to  make.  Kept  indoors,  as  works  of  art  are,  it  would  last  a 
very  long  time.  It  is  not  the  most  durable  varnish  that  can 
be  made,  but  is  the  most  durable  brilliant  varnish.  Contain- 
ing a  large  proportion  of  oil  its  flowing  qualities  are  second  only 
to  that  of  oil  itself;  and  it  is  applied  as  a  heavy  flowing  coat 
with  a  large,  thick  brush  of  the  finest  hair.  Like  every  difficult 
operation  of  art  it  is  only  to  be  learned  by  observation  and  practice. 
It  is  the  finish  and  crown  of  all  the  work  which  has  gone  before. 

Keep  the  Carriage  Warm,  Dry,  and  Clean. — When  it  is 
done  the  structure  is  left  at  rest  in  a  dry,  warm,  clean  room  for 
a  day ;  then  it  is  dry*  enough  so  that  dust  will  not  stick  to  it  easily, 
and  it  may  be  removed  to  another  dry,  warm,  clean  room  to 
remain  until  it  is  thoroughly  dry  and  hard.  Varnish,  while 
drying,  must  always  be  kept  warm,  and  of  an  even  temperature, 
not  exposed  to  sudden  changes  of  any  sort,  and  dry  as  well  as 
clean.  A  damp  atmosphere,  sometimes  unavoidable  because  of 
the  climate,  is  a  fruitful  source  of  trouble.  Dirt  and  dust  are 
the  great  adversary,  and  there  is  no  peace  in  this  life  for  the 
varnish-user  who  cannot  overcome  them.  When  one  reads  of 
the  Chinese  and  Japanese  lacquers  which  harden  in  rooms  with 


310  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

wet  floors  and  the  walls  hung  with  wet  sheets  he  is  moved  to  envy. 
The  heathen  Chinee  certainly  does  accomplish  wonderful  things 
in  this,  and  perhaps  we  may  have  to  learn  from  him;  though 
it  is  believed  by  many  that  there  are  just  as  great  heathen  engaged 
in  the  varnish  business  in  this  country  as  there  are  anywhere. 

Shorter  Methods. — It  is  not  here  asserted  that  every  grocer's 
delivery  wagon  is  finished  with  the  elaborate  detail  which  has 
been  described.  There  are  many  short  cuts  to  economy.  For 
instance,  it  is  very  common  to  omit  the  use  of  rough- stuff.  The 
work  is  primed,  given  a  coat  of  rub-lead  (which  may  be  tinted 
the  color  of  the  paint  which  is  to  follow),  sandpapered,  painted, 
and  given  a  coat,  not  of  rubbing- varnish,  but  of  finishing- varnish ; 
and  good  durable  varnishes  are  made  at  a  less  cost  than  wearing- 
body.  Such  a  finish  is  not  as  smooth  or  brilliant  as  a  more  costly 
one,  but  it  may  be  reasonably  durable.  Rough- stuff  is  very 
commonly  omitted  on  the  running- gear  of  carriages,  especially 
on  the  wheels,  as  being  too  hard  and  possibly  brittle.  The 
running-gear  is  made  up  of  pieces  with  curved  surfaces.  These 
are  much  more  shiny  than  flat  ones,  hence  require  less  work  to 
make  them  look  well.  Gears  are  usually  finished  with  a  darker, 
and  therefore  cheaper  varnish  than  that  used  on  the  carriage- 
body.  There  is  no  limit  to  the  ingenuity  which  has  been  dis- 
played in  inventing  cheap  ways  to  refinish  wagons  and  still  have 
them  look  well  enough  to  be  accepted  by  the  owners.  Even  the 
railroad- coach  painters  can  take  lessons  from  the  carriage  men 
in  this.  As  Denham's  couplet  has  it : 

"  They  varnish  all  their  errors,  and  secure 
The  ills  they  act,  and  all  the  world  endure." 

But  these  things  are  out  of  place  here.  The  aim  of  the  fore- 
going sketch  of  the  subject  is  to  tell  the  uninstructed  but  inter- 
ested inquirer  the  general  methods  employed  by  good  workmen, 
the  principles  of  which  are  common  to  all  the  high- class  shops, 
whose  works  do  praise  them;  and  of  whom  we  may  say,  with 
Shakespeare : 

"We'll  put  on  those  shall  praise  your  excellence, 
And  set  a  double  varnish  on  the  same." 


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CHAPTER  XX. 

HOUSE-PAINTING. 

THE  most  important  branch  of  the  art  of  painting  is  that  which 
relates  to  the  protection  and  decoration  of  houses,  by  far  the 
greatest  portion  of  which  are  built  of  wood,  and  those  which  are 
said  to  be  of  brick  or  stone  are  largely  of  wood,  having  wooden 
floors,  doors,  and  door-  and  window- casings.  Oil  paints  are 
almost  universally  used  on  the  exterior  woodwork,  and  very 
largely  within.  Varnishes  are  also  used  on  the  interior,  and  in 
the  bettef  class  of  houses  enamel  paints  are  used  to  a  considerable 
extent.  Ceilings  sometimes  receive  an  alleged  de  oration  with 
fresco  or  distemper  paints,  but  the  less  said  about  that  the  better. 
It  is  only  palaces  and  very  fine  houses  which  should  be  decorated 
in  fresco. 

The  vast  majority  of  houses  in  this  country  are  painted  with 
white-lead  paint,  either  pure  or  (more  commonly)  adulterated 
with  barytes  (barium  sulphate),  terra  alba  (sulphate  of  lime), 
whiting  (carbonate  of  lime),  or  other  less  important  sophisti- 
cations. Carbonate  of  barium  is  sometimes  used  instead  of  the 
sulphate.  These  barium  compounds  are  the  least  objectionable, 
being  in  fact  substances  chemically  inert  and  of  stable  composi- 
tion ;  but  they  are  practically  without  coloring  power,  being  nearly 
transparent  in  oil,  and  while  they  probably  help  to  protect  the 
wood  they  are  really  used  only  to  cheapen  the  paint,  and  commonly 
to  increase  the  profit  to  the  maker  or  dealer;  not  at  all  for  a  benefit 
to  the  consumer.  The  latter  is  not  an  object  of  unreserved  pity; 
he  gets  these  things  because  he  is  unwilling  to  pay  a  fair  price 
for  the  more  economical  material,  and  this  because  of  his  ignorance. 

White  zinc  is  also  an  important  and  valuable  white  paint; 


312  TECHNOLOGY  OF   PAINT  AND    VARNISH. 

zinc  paint  is  harder  than  lead  paint,  and  a  mixture  of  zinc  is 
therefore  regarded  by  many  as  better  than  pure  lead,  especially 
for  finishing- coats.  It  is  commonly  thought  to  be  of  a  purer 
white  than  white  lead,  and  is  largely  used  on  interior  work  espe- 
cially; when  added  to  white  lead  it  is  usually  in  the  proportion 
of  one-third  zinc  to  two-thirds  lead. 

Very  many  houses  are  painted  white,  but  more  commonly 
with  some  light  color  made  by  the  addition  of  a  tinting  material 
to  the  white  paint.  Some  of  these  tinted  paints  are  fast  to  light. 
This  is  commonly  true  of  the  grays,  and  of  those  yellows  which 
contain  ochre,  and  all  those  paints  tinted  with  the  iron  oxides; 
but  yellows  tinted  with  chrome  yellow,  or  colors  made  with  chrome 
green  or  Prussian  blue,  are  fugitive,  and  light  shades  of  these 
colors  should  be  avoided  for  exteriors. 

White  lead  is  usually  sold  as  "paste  white  lead"  ground 
with  10  per  cent,  of  linseed- oil,  and  when  obtained  in  this  form 
from  the  manufacturers  of  white  lead  (who  are  sometimes  but 
not  usually  makers  of  prepared  paints)  is  always  pure,  so  far  as 
my  experience  goes.  This  should  be  thinned  with  pure  linseed- oil. 

Do  Not  Use  Thinners. — No  turpentine  or  benzine  should  ever 
be  allowed  about  the  premises  where  this  work  is  going  on.  Most 
of  the  failures  of  lead  and  zinc  paints  are  due  to  the  use  of  these 
volatile  thinners.  If  raw  linseed- oil  is  used  it  may  be  desirable 
to  add  5  per  cent,  of  a  good  drier.  This  should  be  pale  in  color, 
indicating  that  it  has  been  made  at  a  low  temperature,  and  should 
be  free  from  rosin.  The  latter  is  not  an  easy  thing  to  detect,  but  if 
a  fair  price  is  paid,  say  $1.50  to  $2  a  gal.  at  retail,  and  freedom 
from  rosin  is  guaranteed  by  a  maker  of  good  reputation,  the  buyer 
ought  to  be  safe.  For  the  benefit  of  the  maker  of  paints  it  may 
be  said  that  such  driers  are  made  usually  of  oil,  combined  with 
much  lead  and  a  little  manganese.  Japan  driers  containing  resins 
(not  rosin)  are  also  excellent,  but  their  price  is  high  if  they  are 
of  good  quality.  There  are  some  low- temperature  manganese 
driers  which  have  a  good  name,  but  the  black  or  very  dark  japan 
driers  are  to  be  avoided,  for  they  injure  the  durability  of  the 
paint.  Every  bit  of  drier  you  use  is  a  damage  to  you,  and  the 


HOUSE-PAINTING.  3 1 3 

lack  of  it  is  fatal,  for  the  paint  certainly  must  dry  in  a  reasonable 
time. 

Dark  Colors  Most  Durable. — Paints  made  with  white  lead  and 
white  zinc  as  a  basis  are  good  paints,  but  there  are  more  durable 
paints  (for  wood)  made  of  other  pigments.  The  ochres,  umber, 
sienna,  and  the  iron  oxides  in  general  are  far  more  permanent, 
and  to  paints  the  color  of  which  will  admit  the  use  of  an  appreci- 
able amount  of  lampblack  this  latter  pigment  imparts  a  high 
degree  of  stability »  There  is  no  paint  so  lasting  on  wood  as 
black  paint  made  with  lampblack  as  the  coloring-matter.  A 
great  variety  of  subdued  yellows,  browns,  and  reds  may  be  made 
which  will  outlast  the  lead  or  zinc  paints.  Sometimes,  where  the 
final  color  can  only  be  had  by  one  of  the  latter,  the  priming-coat 
and  the  second  may  be  of  the  former  with  advantage.  They  are 
also  cheaper.  Lead  and  zinc  are  expensive  pigments,  and  a  white- 
lead  paint  weighs  20  Ibs.  to  the  gallon  when  ready  for  use,  while 
oxides  weigh  about  12  Ibs.  per  gallon. 

Knots. — Pine  wood  usually  contains  knots,  some  of  which  are 
full  of  pitch,  and  this  pitch  will  penetrate  any  oil  paint  or  oleo- 
resinous  varnish  and  make  a  bad  spot.  These  knots  may  be 
covered  with  shellac  varnish,  on  which  the  pitch  does  not  act, 
before  painting.  Some  of  the  liquids  distilled  from  pine  wood, 
of  which  many  are  on  the  market,  are  also  said  to  be  efficient  for 
this  purpose.  Some  woods,  southern  pine  in  particular,  are  very 
bad  to  paint  because  of  the  pitch  they  contain,  which  makes  the 
paint  peel  off;  and  this  should  be  remembered  when  passing 
judgment  on  a  job  of  painting  which  has  not  lasted  well.  If 
shellac  is  used  for  stopping  knots  it  is  common  to  use  white  shellac 
if  a  very  light  paint  is  to  be  used  over  it;  but  if  the  paint  is  dark 
use  orange  shellac  because  it  is  a  better  varnish  than  white  shellac. 
The  latter  must  be  used  if  the  wood  is  to  be  finished  in  the  natural 
colors  with  varnish. 

Priming-coat. — If  a  coat  of  good  thick  paint  is  applied  to  a 
fresh  surface  of  wood  the  oil  is  absorbed,  leaving  the  pigment 
without  enough  binding  material.  For  this  reason  it  is  proper  to 
first  prepare  the  surface  of  the  wood  before  the  paint  is  applied. 


314  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

This  is  called  filling  the  surface ;  in  reality  it  is  filling  the  pores, 
and  the  material  used  is  called  a  filler.  The  best  filler  for  wood 
which  is  to  receive  ordinary  oil  paint  is  a  coat  of  pure  raw  linseed- 
oil.  After  this  has  disappeared  in  the  wood  a  coat  of  very  thin 
paint  may  be  applied.  Sometimes  this  second  coat  is  also  pure 
oil,  but  if  pigment  is  added  very  little  should  be  used. 

Putty. — After  the  wood  is  thus  filled,  or  primed,  is  the  time  to 
putty  up  all  nail- holes  and  other  defective  places.  Ordinary  putty 
should  not  be  used  for  this,  but  only  white- lead  putty,  made  of 
paste  white  lead  with  enough  dry  white  lead  worked  into  it  to 
make  it  stiff  enough  to  suit  the  workman.  This  is  better  than 
the  best  common  putty,  which  is  made  of  whiting  or  ground 
chalk  mixed  with  linseed-oil,  and  if  honestly  made  is  very  durable ; 
but,  cheap  as  this  is,  it  is  made  cheaper  by  using  inferior  oil,  and 
it  is  now  very  difficult  to  get  any  pure  putty.  It  is  therefore  very 
important  to  use  white-lead  putty,  which  may  be  tinted  to  match 
the  paint.  On  outside  painted  work  it  is  perhaps  allowable  to 
apply  putty  with  a  steel  putty- knife;  but  on  interior  work  a 
wooden  stick  or  spatula  must  be  used,  so  as  not  to  mar  the  surface. 
Putty  should  never  be  applied  to  the  natural  surface  of  the  wood, 
since  that  would  absorb  part  of  the  oil  and  leave  the  putty  dry 
and  friable;  the  wood  must  first  be  primed. 

The  surface  is  now  ready  to  be  painted,  and  should  receive 
at  least  two  good  coats  of  paint,  sufficient  time  to  dry  being  allowed 
between  coats.  If  the  window- casings  and  other  raised  surfaces 
are  to  be  painted  a  different  color  from  the  body  of  the  house,  it 
is  well  to  do  this  first;  the  body-color  may  then  be  laid  neatly  up 
to  the  other.  It  is  a  good  plan  to  paint  the  back  or  interior  sur- 
face of  all  window-  and  door- casings  before  they  are  erected  with 
a  cheap  oxide  paint,  made  with  pure  linseed-oil;  this  will  prevent 
warping  and  distortion.  This  is  not  commonly  done  except  on 
fine  houses,  but  it  is  desirable. 

Area  Covered. — A  gallon  of  paint  ought  not  to  cover  more  than 
500  sq.  ft.,  and  a  gallon  of  priming-coat  not  more  than  300;  as 
a  matter  of  fact,  for  outside  painting  a  gallon  does  not  cover  as 
much  as  this. 


HO  USE-PAIN  TING.  3  J  5 

The  foregoing  directions  apply  to  the  most  common  sort  of 
exterior  painting.  Nothing  has  been  said  about  the  use  of  varnish 
in  paint  for  this  purpose,  but  in  fact  the  best  makers  of  house- 
paints  are  large  buyers  of  varnish,  the  addition  of  which  increases 
the  durability  and  improves  the  appearance  of  the  paint.  It  makes 
it  glossy,  so  that  dirt  does  not  so  easily  adhere  to  it.  If  varnish 
is  used  for  this  purpose  it  ought  to  be  good  varnish,  and  this  will 
increase  the  cost  of  the  paint. 

Interior  Woodwork. — The  treatment  of  the  interior  woodwork 
is  much  more  complicated.  It  should  be  thoroughly  seasoned 
and  dry  before  any  finishing  is  done,  and  should  be  sandpapered 
to  an  even  surface,  all  sandpapering  to  be  done  with  the  grain  of 
the  wood.  As  recommended  for  window-  and  door-casings,  the 
back  of  all  interior  woodwork  must  be  thoroughly  painted  with  a 
good,  durable  linseed- oil  paint,  thin  enough  to  serve  as  a  priming- 
coat.  This  must  be  done  immediately  after  the  pieces  are  delivered 
on  the  premises.  The  first  coat  of  filler  must  also  be  applied  to 
the  front  or  outer  surface.  In  this  way  the  absorption  of  moisture 
will  be  prevented;  and  all  this  should  be  done  before  the  work 
has  been  allowed  to  remain  overnight  on  the  premises.  This 
may  seem  somewhat  exacting,  but  we  should  remember  that 
neglect  of  this  precaution  may  impair  the  value  of  the  material 
during  its  whole  service.  The  most  important  of  all  things  is  to 
start  right.  The  first  coat  of  filler  is  usually  linseed-oil,  and  this 
may  be  applied  very  rapidly. 

Fillers. — There  are  two  sorts  of  fillers  made:  liquid  fillers  and 
paste  fillers.  The  former  are  commonly  rosin  compounds,  and 
never  should  be  used  for  any  purpose.  If  a  liquid  filler  must  be 
used,  fill  the  wood  completely  with  raw  or  boiled  linseed-oil,  or 
with  a  good  varnish.  The  very  best  filler  that  can  ever  be  put  on 
wood  is  a  good  varnish;  but  this  is  not  what  is  commonly  meant 
by  a  filler.  Paste  fillers  are  a  sort  of  paint;  the  best  have  pul- 
verized quartz  as  the  solid  part,  corresponding  to  the  pigment, 
and  the  liquid  is  a  quick-drying  varnish.  Only  enough  liquid  is 
used  to  make  a  sort  of  paste,  and  before  applying  this  is  mixed 
with  spirit  of  turpentine  to  such  a  consistency  that  it  can  be  applied 


3 1 6  TECHNOLOGY  OF   PAINT  AND    VARNISH. 

with  a  short,  stiff  bristle  brush,  and  it  must  be  rubbed  well  into 
the  pores  of  the  wood.  In  about  half  an  hour  it  will  be  found  to 
have  set,  and  the  excess  must  then  be  rubbed  off  clean,  first  with 
excelsior  (fibrous  wood- shavings)  and  then  with  felt,  rubbing 
across  the  grain  of  the  wood  so  as  to  force  the  filler  into  the  pores. 
It  is  practically  impossible  for  the  amateur  to  make  as  good  a 
filler  as  he  can  buy.  The  pigment  must  be  ground  fine,  yet  it 
should  not  be  so  fine  as  to  have  too  little  grit,  and  the  mixing  of 
a  varnish  to  have  just  the  right  properties  is  a  difficult  matter.  No 
better  advice  is  possible  to  any  one  desiring  to  experiment  in  this 
direction  than  to  get  the  best  paste  filler  on  the  market  and  try 
to  match  it.  Wood-fillers  may  be,  and  usually  are,  stained  by 
the  addition  of  oil-stains  to  the  color  of  the  wood,  or  to  the  color 
desired  by  the  designer.  This  is  done  when  they  are  finally 
thinned  before  using.  These  oil-stains  are  really  paints  made 
with  selected  pigments  of  extraordinary  fineness,  and  may  be 
added  to  or  thinned  with  oil,  varnish,  or  turpentine.  Such  pig- 
ments are  used  as  are  somewhat  transparent  but  have  a  deep 
and  brilliant  color;  great  staining- power,  but  not  great  opacity. 
Raw  (unroasted)  sienna  may  be  regarded  as  a  typical  pigment  of 
this  class. 

The  practice  of  filling  wood  completely  with  varnish  has  been 
recommended.  It  is  a  very  old  method.  It  is  natural  that  those 
who  do  this  should  wish  to  use  a  cheaper  varnish  for  this  use  than 
that  with  which  they  finish ;  also  that  they  should  want  a  varnish 
which  will  dry  quickly.  The  combination  of  these  qualities,  car- 
ried to  the  extreme,  results  in  a  rosin  varnish  loaded  with  driers; 
and  this  is  what  is  meant  now,  in  the  trade,  by  a  liquid  filler. 
Rosin,  with  little  oil,  requires  very  little  turpentine  or  benzine  to 
make  it  a  thin  liquid;  in  fact  pale  rosin  is  almost  a  liquid  already, 
so  that  a  varnish  of  this  sort  has  very  little  volatile  matter  in  it  and 
consequently  fills  up  the  pores  of  the  wood  very  quickly,  and  dries 
almost  as  a  spirit  varnish  does  by  the  evaporation  of  the  solvent. 
But  no  good  ought  to  come  to  the  man  who  puts  such  a  compound 
on  a  piece  of  wood  which  is  afterward  to  be  varnished  with  decent 
material. 


HOUSE-PAINTING.  317 

A  good  paste  filler,  on  the  other  hand,  has  just  as  much  solid 
matter  in  it  as  possible,  and  what  cementing  material  there  is 
may  be  of  first-rate  quality.  There  is  so  little  of  it  anyway  that  it 
is  not  expensive  to  have  it  good. 

Object  of  Filling. — The  object  in  using  a  paste  filler  is  to  fill 
the  pores  of  the  wood  with  solid  matter,  so  that  the  surface  to  be 
varnished  shall  be  without  any  soft  and  absorbent  places,  but 
hard  and  glassy.  The  filler  is  rubbed  into  the  wood  when  it  is 
applied,  and  when  it  has  hardened  it  is  rubbed  so  that  all  that  can 
be  crowded  into  the  wood  may  remain,  and  the  surplus  be  taken  off. 
This  is  also  the  way  furniture  is  treated;  but  rubbing- varnishes 
are  then  sometimes  used  on  furniture,  while  they  should  not  be 
used  on  the  woodwork  of  houses,  which  should  be  varnished  with 
at  least  three  coats  of  a  moderately  elastic  varnish,  made  with  20 
gals,  of  oil  to  100  Ibs.  of  resin.  Not  less  than  a  week  should 
elapse  between  coats.  It  is  best  to  sandpaper  the  first  coat  with 
very  fine  sandpaper,  and  the  second  coat,  when  dry,  should  be 
rubbed  with  curled  hair  until  the  gloss  is  removed.  These  pre- 
cautions secure  a  more  perfect  union  between  the  different  coats, 
and  a  more  perfect  surface.  After  the  last  coat  has  become  quite 
hard,  if  the  glossy  surface  is  not  liked,  it  may  be  rubbed  with 
powdered  pumice  and  water,  with  a  piece  of  thick  felt,  until  the 
gloss  is  removed.  Four  coats  of  varnish  are  better  than  three, 
and  if  a  wood- filler  has  not  been  used  four  coats  are  necessary. 

Exterior  Varnished  Work. — Exterior  woodwork,  such  as  out- 
side doors,  railings,  and  the  like  should  never  receive  any  filler, 
which  lessens  the  durability  of  the  varnish,  but  should  be  treated 
with  not  less  than  four  coats  of  spar  varnish  or  a  varnish  made 
on  the  same  lines  as  spar;  that  is,  the  wood  should  be  both  filled 
and  varnished  with  the  same  material.  There  is  no  objection  to 
a  preliminary  coat  of  oil,  which  should  have  plenty  of  time  to 
dry.  Usually  it  is  most  convenient  to  apply  oil  for  the  preliminary 
coat,  which  is  to  hinder  the  hygroscopic  action  of  the  wood,  and 
is  put  on  before  or  immediately  after  the  woodwork  has  been 
brought  on  the  premises;  and  all  inside  blinds,  window-sills,  and 
jambs,  in  fact  everything  exposed  to  the  direct  rays  of  the  sun, 


3i8  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

must  be  treated  as  exterior  woodwork.  Outside  blinds  are  painted 
with  the  same  kind  of  paint,  though  not  the  same  color,  as  the 
outside  of  the  house. 

Interior  Enamel  Painting. — If  any  of  the  interior  woodwork 
is  to  be  finished  in  white  enamel  paint  (or  any  light- colored 
enamel),  it  should  be  well  painted  with  pure  white  lead  and 
linseed-oil  This  should  be  done  according  to  the  directions  for 
outside  work.  It  is  allowable,  however,  to  add  some  spirit  of 
turpentine  instead  of  all  oil,  as  this  makes  the  paint  dry  more 
quickly,  and  on  interior  work  will  be  sufficiently  durable.  Two 
coats  of  white  enamel  paint  are  to  be  applied  for  a  finish.  The 
question  may'  arise,  why  not  do  all  the  painting  with  enamel 
paint?  Because  the  oil  paint  contains  more 'pigment  and  less 
vehicle,  and  hence  is  much  more  opaque  than  enamel.  It  is 
cheaper  by  the  gallon,  very  much  cheaper  in  labor,  far  more 
rapid,  and  is  good  enough.  Two  coats  of  an  enamel  paint  applied 
to  a  good  white  under- coat,  which  should  consist  of  a  priming- 
coat  and  two  full  coats,  will  give  a  beautiful  surface.  The  first 
of  these  enamel  coats  should  be  rubbed  with  curled  hair,  and 
the  second  may  be  finished  to  suit  the  owner. 

Floors. — Floors  are  a  source  of  endless  trouble.  Soft-wood 
floors  are  sometimes  painted,  and  this  is  easy,  for  when  the  paint 
wears  off  it  can  be  renewed.  Some  soft-wood  floors  are  stained. 
The  best  way  to  do  this  is  to  thin  down  an  oil-stain  with  spirit  of 
turpentine  and  color  it.  The  stain  sinks  into  the  wood  and  cannot 
be  removed,  except  as  the  wood  wears  off.  The  floor  can  then  be 
varnished.  If  it  has  already  been  filled  with  varnish  the  stain 
cannot  get  in;  then  the  easiest  way  is  to  add  some  oil- stain  to  a 
floor  varnish  and  apply  it.  Hard-wood  floors  are  not  stained, 
but  are  varnished  to  show  the  natural  color  of  the  wood,  and 
look  very  fine  when  new,  but  the  soles  and  especially  the  nail- 
clad  heels  of  shoes  will  wear  the  varnish  off  after  a  little;  not 
all  over  the  floor  but  near  doors  and  wherever  people  continually 
pass.  The  margins  of  the  floor  are  all  right  but  the  worn  places 
'  look  badly,  and  if  not  attended  to,  dirt  gets  into  the  grain  of  the 
wood  and  can  hardly  be  removed.  If  these  places  are  revarnished 


HO  USE-PA  IN  TING.  3  *  9 

and  the  rest  of  the  floor  left  untouched  a  spotty  appearance  is 
produced;  but  the  owner  may  be  consoled  by  rinding  that  if  the 
varnish  is  rubbed  out  thin  around  the  edges  of  the  newly  var- 
nished places  it  does  not  show  so  much,  and  after  a  week  or  two 
is  not  at  all  conspicuous;  and  in  the  judgment  of  the  writer  this 
is  better  than  to  pile  up  varnish  on  those  parts  of  the  surface 
which  do  not  need  it.  The  art  of  varnishing  a  floor  is  not  very 
difficult,  and  there  ought  always  to  be  some  one  about  a  house 
with  energy  enough  to  do  such  work  in  case  of  emergency.  A 
good  floor  varnish  dries  rapidly.  If  a  thin  coat  is  put  on  at  night 
it  is  hard  enough  to  use  next  day.  White  shellac  varnish  is 
very  often  used  on  floors,  chiefly  because  it  dries  almost  immedi- 
ately. It  is  in  fact  a  very  good  floor  varnish ;  but  it  is  not  nearly 
as  durable  as  a  good  oleo- resinous  varnish,  and  the  chief  trouble 
about  floors  is  that  the  best  varnish  is  short-lived.  Factory 
floors  are  sometimes  covered  with  galvanized  sheet  iron,  and 
this  wears  out  after  a  time;  so  it  must  surprise  no  one  to  have  a 
coating  of  varnish  wear  off,  especially  as  it  is  only  a  tenth  part  as 
thick  as  the  sheet  iron.  We  must  not  expect  to  walk  continuously 
for  many  months  on  a  layer  of  anything  which  is  only  two  or 
three  thousandths  of  an  inch  in  thickness. 

A  filler  should  never  be  used  on  a  floor,  which  should  be 
thoroughly  saturated  with  oil  and  varnish.  The  latter  should 
be  fairly  hard;  as  it  is  not  exposed  to  the  weather  it  is  not  likely 
to  crack,  and  a  soft  varnish  does  not  wear  as  well  as  a  hard  one. 
It  may  contain  12  to  18  gals,  of  oil  to  100  Ibs.  of  resin.  Less 
oil  makes  it  brittle;  more  makes  it  soft.  It  would  probably  be  a 
good  plan  to  use  a  good  varnish- remover  once  in  five  or  six  years 
and  take  off  all  the  paint  and  varnish  from  a  floor  and  begin  anew. 
Since  the  improvements  in  these  preparations,  paint  and  varnish 
can  be  easily  removed  without  the  danger  of  fire  which  attends 
the  use  of  a  gasoline  torch  in  a  furnished  house. 

Floor  Wax. — There  is  still  another  way  to  treat  a  floor,  which 
is  by  the  use  of  wax.  The  wax  is  made  into  a  paste  with  spirit 
of  turpentine  and  the  floor  is  thoroughly  filled  with  it.  This  is  a 
rather  laborious  job  and  takes  some  time.  The  brushes  used 


320  TECHNOLOGY   OF   PAINT  AND    VARNISH. 

for  rubbing  in  and  polishing  the  wax  are  large  and  stiff.  They  are 
weighted  with  heavy  iron  backs  and  are  attached  to  a  long  handle. 
The  floor  ought  to  be  polished  with  this  brush  daily,  and  twice 
a  month  a  little  fresh  wax  should  be  added.  A  properly  kept 
waxed  floor  is  very  handsome.  It  looks  rather  better  than  a  well- 
varnished  one,  but  it  requires  a  great  deal  of  attention,  and  if 
neglected  nothing  can  look  worse;  and  after  a  floor  has  been 
well  waxed  it  is  difficult,  some  think  impossible,  to  wash  it  out 
so  that  it  will  take  varnish.  A  waxed  floor  in  good  condition 
is  also  very  slippery,  sometimes  almost  dangerously  so ;  rugs  slide 
around  on"  it  like  boards  on  ice.  But  it  certainly  is  a  beauti- 
ful finish,  and  protects  the  wood;  and  the  necessity  of  keeping 
it  rewaxed,  if  it  is  to  look  well,  makes  it  necessary  to  do  it  by 
domestic  labor,  and  this  tends  to  keep  the  floor  in  condition. 
It  is  rather  hard  work  to  use  the  polishing-brush  efficiently. 

The  wax  used  is  not  commonly  beeswax,  but  a  vegetable 
wax  called  carnauba  wax,  harder  than  beeswax.  Floorwax 
is  not  a  simple  substance,  but  the  best  preparations  are  appar- 
ently rather  complex;  each  maker  has  his  own  formula.  Bees- 
wax is  sometimes  used;  but  the  carnauba- wax  mixtures  are  less 
sticky,  and  much  superior  to  it  in  every  way.  Printed  direc- 
tions are  furnished  by  the  makers,  and  may  be  carried  out  by 
any  one  of  ordinary  intelligence.  Wax  finishes  are  sometimes, 
though  rarely,  used  on  interior  woodwork,  but  not  on  stair- 
rails,  nor  on  furniture.  They  can  be  applied  to  floors  which 
have  been  varnished,  if  the  varnish  has  worn  or  been  scrubbed 
off.  The  fact  that  the  wood  is  filled  with  varnish  is  no  objection. 
In  fact  the  directions  for  using  wax  usually  advise  filling  the 
wood  before  waxing. 

Metal  Roofs  and  Gutters. — Tin  roofs  and  metal  gutters  and 
leaders  have  been  a  source  of  trouble  from  time  immemorial. 
The  painter's  tradition  is  that  tin  roofs  cannot  be  painted  until 
they  have  stood  long  enough  to  become  rusty;  then  the  paint 
will  adhere.  This  is  "flat  burglary  as  ever  was  committed." 
It  is  true  that  paint  does  not  adhere  well  to  new  tin.  The  reason  is 
.that  new  tin  is  greasy,  or  covered  with  some  chemical  substances 


HO  USE-PA  IN  TING.  321 

which  are  inimical  to  paint.  Tin  plate,  it  is  well  known,  is  made 
from  thin  iron  plates  (called  " black  plates")  by  dipping  them 
in  a  bath  of  melted  tin;  in  the  same  way  galvanized  iron  is  made 
by  dipping  iron  in  melted  zinc.  But  the  melted  metal  will  not 
adhere  to  the  iron  unless  the  latter  is  chemically  clean.  This  is 
effected  by  dipping  it  in  acid,  from  which  it  goes  to  the  bath  of 
hot  metal.  A  little  acid  is  in  this  way  carried  over,  and  thus  is 
formed  a  film  of  chloride  or  sulphate  of  tin  or  zinc,  which,  in 
an  anhydrous  and  melted  condition,  floats  on  top  of  the  bath, 
and  as  the  coated  plates  emerge,  a  little  of  this  compound  sticks 
to  them.  This  is  powerfully  corrosive,  and  will  destroy  any 
paint.  Another  trouble  is  caused  by  the  practice  some  makers 
have  of  covering  the  melted  metal  with  hot  oil,  usually  palm-oil, 
to  prevent  the  air  from  getting  at  it;  and  as  the  plates  come 
through  they  get  a  final  coating  of  hot  oil.  Still  another  prac- 
tice is  that  of  hanging  the  coated  tin  plates  in  hot  oil  to  drain. 
In  some  of  these  ways  nearly  all  tin  and  galvanized  iron  is  coated 
with  something  which  prevents  the  adhesion  of  paint.  The 
remedy  is  obvious.  Clean  the  roof  before  you  paint  it.  It 
ought  to  be  thoroughly  scrubbed  with  soap  and  water.  The  addi- 
tion of  sand  makes  a  more  thorough  job.  Some  rub  the  metal 
well  with  coarse  cloths,  such  as  burlap,  well  wet  with  benzine. 
If  soap  and  water  are  used,  the  scrubbing  should  be  followed 
by  a  thorough  rinsing  with  clean  water,  and  of  course  the  roof 
should  be  dry  when  painted.  By  following  these  directions, 
tinned  and  galvanized  metal- work  may  be  painted;  and  aside 
from  these  directions  the  methods  and  materials  employed  on 
structural  steel  should  be  used.  It  is  a  wise,  though  not  very 
usual,  practice  to  paint  the  lower  side  of  the  tin  before  laying 
it  on  the  roof.  This  prevents  corrosion  from  below.  New 
metal  roofs  should  receive  three  coats  of  a  highly  elastic  varnish 
or  paint;  probably  four  would  be  economical,  for  they  will  almost 
certainly  be  neglected.  They  are  exposed  to  very  severe  con- 
ditions, and  a  varnish  or  paint  too  elastic  or  soft  to  be  used  almost 
anywhere  else  will  grow  hard  under  the  heat  and  intense  chemical 
action  of  the  rays  of  the  sun.  There  are  plenty  of  compositions 


.322  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

.sold  for  painting  these  surfaces,  the  secret  of  which  lies  in  fol- 
lowing directions  essentially  like  those  just  given,  by  which  any 
.good  paint  may  be  made  to  adhere.  They  are  like  the  drugs 
which  are  sold  to  cure  the  tobacco  habit,  which  will  certainly 
cure  if  taken  according  to  directions,  one  of  which  is  that  the 
patient  shall  abstain  from  the  use  of  tobacco  for  a  term  of  some 
years;  so  if  these  metal  paints  are  used  strictly  as  prescribed 
they  will  stick.  No  doubt  they  will,  if  they  are  good  for  any- 
thing. 

Fire-proof  Paints. — Shingled  roofs  are  sometimes  painted 
ivith  what  are  called  fire-proof  paints.  No  paint  is  really  fire- 
proof, but  it  may  be  made  to  retard  the  spread  of  fire.  If  a  roof  is 
painted  with  something  which  will  prevent  its  being  set  on  fire 
by  a  burning  fragment  carried  by  the  wind  from  some  other  build- 
ing, it  must  be  conceded  that  a  substantial  gain  has  been  secured, 
and  this  can  probably  be  effected.  In  the  first  place  it  must  be 
remembered  that  any  oil  or  varnish  is  in  its  original  condition 
highly  combustible;  that  combustion  is  a  process  of  oxidation; 
that  oil  and  varnish  dry  by  oxidation,  and  hence  that  when  they 
are  thoroughly  dry  they  are  far  less  easily  set  on  fire  than  when 
fresh;  hence  it  is  not  fair  to  test  a  fire-proof  paint  until  it  is  thor- 
oughly dry.  Any  good  paint  may  be  made  more  resistant  to 
fire  by  adding  to  each  gallon  of  it  J  Ib.  or  i  Ib.  of  boric  (boracic) 
acid.  This  is  a  solid  substance  which  is  purchased  in  the  form  of 
a  powder  or  flakes.  When  subjected  to  heat  this  fuses  and 
forms  a  sort  of  glass,  and  this  protects  the  wood  from  the  access 
of  air;  also  it  is  slowly  converted  into  vapor,  and  this  forms  a 
protective  coating  over  the  roof,  for  if  the  air  cannot  get  to  the 
wood  the  latter  may  be  heated  so  as  to  char,  but  it  will  not  burn, 
and  this  is  just  what  takes  place.  Some  of  the  patented  paints 
contain  instead  of  boric  acid  some  very  easily  fusible  glass,  pow- 
dered. The  glass  melts  with  the  heat  and  protects  the  wood. 
Ordinary  glass  will  not  answer;  and  this  extra-fusible  glass  is 
open  to  the  same  objection  as  boric  acid,  in  that  it  is  soluble  in 
water  and  gradually  is  washed  out  by  the  rain;  but,  of  course, 
in  all  cases  the  oil  or  varnish  in  the  paint  keeps  the  rain  from 


HO  USE-PA  IN  TING.  323 

the  soluble  constituents  for  a  considerable  time.     Such  paints 
must  therefore  be  renewed  rather  frequently. 

Sanding. — When  paint  is  partly  dry,  but  while  it  is  still  tacky, 
it  is  sometimes  sanded.  This  is  done  by  sprinkling  dry  sand  over 
its  surface.  The  effect  of  this  is  to  make  a  rough,  hard  surface 
somewhat  resembling  stone  in  appearance.  It  does  not  appear 
to  be  generally  known  that  any  dry  pigment  may  be  mixed  with 
the  dry  sand,  by  tumbling  them  together  in  a  revolving  barrel 
or  by  any  equivalent  means;  by  doing  so  the  grains  of  sand 
receive  a  film  of  dry  paint,  and  when  applied  to  the  painted  sur- 
face an  effect  is  produced  which  is  sometimes  much  better  than 
can  be  had  by  the  use  of  sand  alone.  A  black  varnish,  for  in- 
stance, can  be  thus  made  brown,  olive,  dark  green,  or  almost 
any  dark  color.  If  desired,  a  sanded  coat,  when  thoroughly 
dry,  may  receive  a  very  thin  coat  of  paint  and  be  sanded  again. 
In  this  way  a  very  rough  surface  is  produced.  The  influence  of 
the  sand  in  resisting  abrasion  is  considerable.  Metal  gutters 
and  leaders  on  stone  buildings  can  be  painted  to  match  the  color 
of  the  stone  and  then  sanded,  when  they  are  much  less  con- 
spicuous than  if  treated  in  any  other  way. 

Cellars  are  usually  whitewashed  or  calcimined;  "cold- water" 
casein  paints  are  also  used.  These  the  writer  does  not  recom- 
mend or  disapprove.  In  some  U.  S.  Government  tests  they  are 
said  to  get  mouldy,  but  this  does  not  seem  unavoidable,  as 
some  germicide  ought  to  be  mixed  with  the  paint. 

Plastered  walls  are  sometimes  painted.  These  should  be 
allowed  to  stand  a  year  before  painting  if  possible;  this  is  to 
get  rid  of  caustic  alkali.  They  may  then  be  painted  with  any 
oil  or  varnish  paint.  If  time  cannot  be  allowed,  they  should, 
before  painting,  be  washed  with  a  solution  of  brown  sugar  and 
vinegar  or  acetic  acid,  to  neutralize  the  alkali.  This  is  a  standard 
formula  of  house-painters;  probably  the  sugar  makes  saccha- 
rate  of  lime.  The  author  has  not  experimented  with  it. 

In  general  it  may  be  said  that  thin  coats  of  paint  or  varnish, 
well  brushed  out,  are  more  durable  than  an  equal  amount  of 
material  applied  in  heavy  coats,  and  are  not  so  liable  to  crack; 


324  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

that  varnishes  and  enamel  paints  should  always  be  rubbed  between 
coats  with  curled  hair  or  fine  sandpaper  to  remove  the  gloss,  for 
if  this  is  not  done  the  succeeding  coat  does  not  adhere  properly; 
and  that  on  exterior  work  the  last  coat  of  varnish  or  enamel  should 
be  left  with  the  full  gloss,  as  its  durability  is  impaired  by  removing 
the  gloss  from  the  last  coat.  There  are  three  sorts  of  finish  for 
interior  varnished  or  enamelled  surfaces,  the  first  being  the  least 
and  the  last  the  most  expensive:  they  may  be  left  with  a  full, 
natural  gloss;  they  may  be  rubbed  to  a  dull  finish  with  curled 
hair,  very  fine  sandpaper,  or  pumice  and  water;  or  they  may 
be  first  pumiced  and  then  given  a  high  polish  with  rottenstone 
and  water. 

Above  all  things,  use  good  material.  A  good  varnish  may 
be  had  for  $3  a  gallon  at  retail,  and  will  give  a  finish  that  with 
moderately  good  care  will  last  many  years;  while  a  cheap  varnish 
sold  for  $1.50  or  $2  will  lose  its  lustre  in  a  short  time  and  will  be 
a  positive  eyesore  in  a  year  or  two.  The  former,  even  if  it  cost 
$15  a  gallon,  would  be  cheaper  than  the  latter.  There  are  legiti- 
mate and  proper  uses  for  cheap  varnishes;  but  it  is  a  shameful 
thing  to  put  them  on  a  house  which  people  have  got  to  live  in 
and  look  at,  and  which  is  intended  to  last  for  generations.  Not 
only  is  the  appearance  of  such  things  poor,  but  they  do  not  pro- 
tect the  surface,  which  gets  full  of  dirt  and  germs  of  all  sorts. 
A  good  varnish  or  paint  is  one  of  the  best  aids  to  cleanliness  and 
purity  of  which  we  can  avail  ourselves. 

Putty  for  Windows. — The  use  of  white- lead  putty  has  been 
recommended  for  filling  cracks.  Carriage-makers  mix  a  little 
japan  with  this  to  make  it  dry  quickly,  and  this  may  perhaps 
be  permitted,  though  not  recommended,  for  interior  work,  but 
not  for  exterior  use;  but  white- lead  putty  is  not  advised  for  set- 
ting glass,  because  it  is  so  difficult  to  remove  when  the  glass  is 
broken  and  must  be  renewed.  Regular  putty  is  made  by  working 
pure  linseed-oil  and  whiting,  which  is  ground  chalk,  together 
until  of  the  proper  consistency.  It  is  applied  in  a  plastic  condition, 
but  rapidly  sets  and  finally  becomes  hard  and  is  very  durable. 
But  the  reader  is  advised  that  pure  putty  is  only  to  be  obtained 


HO  USE-PA  IN  TING.  325 

with  great  difficulty.  It  is  adulterated,  or  rather  a  spurious  sub- 
stitute is  made,  by  the  use  of  marble- dust  instead  of  whiting. 
Marble-dust  is  granular  and  harsh,  whiting  is  soft  and  smooth; 
and  the  oil  is  adulterated  with  or  entirely  substituted  by  some 
cheap  mineral  oil  or  rosin  mixture.  If  pure  putty  is  used  the 
amount  used  on  an  ordinary  house  probably  does  not  amount 
to  $i ;  yet  the  use  of  an  inferior  article,  the  removal  and  replace- 
ment of  which  will  cost  from  50  cents  to  $i  per  window,  prob- 
ably gives  a  profit  to  the  contractor  of  25  to  50  cents  on  the  whole 
house.  The  contractor  should  be  required  to  guarantee  the  putty 
for  two  years,  and  of  the  money  due  him  at  least  $i  a  window 
should  remain  unpaid  until  the  guarantee  has  expired.  The 
real  reason  for  this  very  common  and  inexcusable  adulteration 
is  that  sash  are  not  hand-made,  but  factory  made,  and  are  com- 
monly supplied  ready  glazed,  so  that  the  sash-maker  is  the  man 
who  buys  the  putty,  and  he  buys  it  in  ton  lots.  Instead  of  paying 
say  $60  a  ton  he  buys  it  for  $30,  and  thus  makes  $30.  To  secure 
this  he  gets  bad  material,  really  much  worse  than  none,  on  fifty 
houses,  at  a  final  cost  to  the  ultimate  purchasers  of  $1,000  or  $2,000 
in  the  aggregate.  The  only  remedy  is  in  requiring  a  guarantee, 
which  the  contractor  may  in  turn  require  from  the  sash-maker. 
There  is  absolutely  no  risk  to  him  if  he  uses  straight  goods.  If 
this  practice  were  generally  adopted  the  manufacture  of  adulterated 
putty  would  immediately  cease.  Putty  is  made  by  machinery; 
but  not  necessarily,  for  any  one  can  make  it  with  no  other  appa- 
ratus than  his  hands,  and  while  hand-made  putty  is  costly  as 
compared  with  the  other,  $3  or  $4  worth  of  labor  would  make  all 
the  putty  needed  for  an  average  house;  so  there  is  no  excuse 
for  using  an  inferior  article. 

Burning-off. — Painted  woodwork,  and  especially  painted  out- 
side doors,  sometimes  require  the  entire  removal  of  the  old  paint 
before  repainting.  The  regular  way  to  do  this  is  by  "burning- 
off."  This  does  not  mean  that  the  paint  is  actually  burned: 
If  this  were  done  the  wood  would  be  charred  and  injured.  It  is 
done  by  the  aid  of  a  painter's  torch,  burning  kerosene  or  naphtha, 
by  which  a  flaring  flame  is  directed  against  the  painted  surface. 


326  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

The  operator  holds  the  torch  in  one  hand  and  a  broad-bladed 
putty-knife  in  the  other.  The  heat  softens  the  old  paint  and  with 
the  putty-knife  or  scraper  he  scrapes  it  off.  The  paint  is  not 
burned  at  all  but  softened  and  loosened  by  heat. 

Paint-removers. — Many  preparations  have  been  tried  for 
removing  old  paint  and  varnish  by  chemical  action,  but  these 
have  never  been  liked  because  the  solution,  which  has  contained 
water  and  alkali,  gets  into  the  wood  and  unfits  it  for  recoating; 
but  lately  a  new  sort  of  paint-  and  varnish- removers  have  come 
on  the  market.  Containing  no  water  and  no  alkali,  they  are  com- 
posed of  wood-alcohol  and  other  alcohols,  benzole,  and  various 
other  liquids,  mixed  together,  and  are  very  efficient.  When  their 
work  is  done  the  surface  may  be  washed  off  with  benzine  and 
is  ready  for  repainting  or  varnishing.  Many  of  the  varnish- 
manufacturers  are  now  selling  compounds  of  this  nature.  They 
are  applied  with  less  risk  and  labor  than  are  involved  in  burning- 
off.  Of  course  they  only  soften  the  old  coat,  which  must  then 
be  scraped  off  in  the  usual  way. 


CHAPTER   XXI. 

FURNITURE-VARNISHING. 

THERE  is  an  art  of  varnishing  furniture  and  similar  belong- 
ings, and  also  a  trade.  The  latter  is  divided  into  many  parts, 
and  concerns  itself  with  supplies  and  methods;  the  former  is  a 
matter  of  principles  and  the  materials  for  their  embodiment. 
" Furniture  varnish"  is  a  term  of  reproach  among  the  varnish- 
makers.  It  is  made  of  " North  Carolina  Zanzibar  gum,"  other- 
wise known  as  common  rosin.  If  there  is  a  normal  price  for  it,  it 
is  about  the  same  as  that  of  spirit  of  turpentine,  but  it  is  often  sold 
for  half  that  sum.  The  writer  has  among  his  archives  a  letter  offer- 
ing a  special  brand  of  it  for  9  cents  a  gallon,  in  barrels,  f.o.b. 
Cleveland,  and  soliciting  permission  to  send  a  barrel  sample  to  a 
large  manufacturer  of  woodenwares.  Nothing  was  said  about  dis- 
counts, and  perhaps  this  is  "rock- bottom."  Lest  this  notice 
should  cause  a  rush  of  trade  to  Cleveland  it  should  be  said  that 
cheap  varnish  is  made  elsewhere.  In  fact,  if  with  New  York  as 
a  centre  and  a  radius  infinity  we  describe  a  circumference,  the 
furniture  varnish-maker  will  be  found  to  flourish  anywhere  within 
the  circumscribed  area. 

In  justice  to  the  furniture-makers  (though  justice  is  about  the 
last  thing  wanted,  or  received  either,  by  the  users  of  so-called 
furniture  varnish),  it  must  be  said  that  a  large  part  of  the  cheap 
stuff  sold  under  the  name  is  used,  not  by  the  furniture  men,  but 
by  painters  of  cheap  houses  for  varnishing  interior  trim,  and  by 
makers  of  cheap  mixed  paints.  It  appeals  to  the  latter  as  being 
cheaper  than  linseed-oil.  As  a  house  varnish,  the  name  has  been 
displaced  largely  of  late  years  by  that  of  "hard  oil-finish,"  but 
the  material  remains  the  same,  though  of  course  some  makers 

327 


328  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

sell  a  pretty  fair  varnish  under  the  latter  name,  just  as  some 
belated  individuals  or  firms  make  furniture  varnish  out  of  var- 
nish-resins and  linseed-oil;  but  they  don't  sell  much  of  it. 

Legitimate  Use  for  Cheap  Varnish. — There  are  two  sides,  and 
usually  more  than  two,  to  most  questions;  and  the  man  who 
makes  kitchen  chairs  says  that  all  the  varnish  is  for  is  to  keep  the 
chair  looking  fresh  until  it  is  sold,  and  that  the  best  varnish  will 
be  scrubbed  off  the  chair  as  quickly  as  soap  and  sand  will  do  it 
after  it  reaches  the  kitchen;  all  of  which  is  true,  and  as  these 
chairs  are  turned  out  at  the  rate  of  a  car-load  a  day  in  some  fac- 
tories the  economy  in  buying  cheap  varnish,  which  is  purchased 
in  car-load  lots,  is  a  substantial  one.  The  varnish  serves  some 
such  a  use  as  the  practice  of  leaving  the  edges  of  books  uncut. 
It  is  a  guarantee  that  the  goods  are  not  second-hand.  The  var- 
nishing of  kitchen  chairs,  by  the  way,  is  done  by  a  method  which 
is  a  refinement  of  simplicity  and  economy.  Many  years  ago  the 
makers  of  agricultural  machinery  found  that  they  could  paint  and 
varnish  their  apparatus  by  dipping  it  in  a  tank  of  paint  or  varnish, 
properly  thinned;  but  the  chair-makers  keep  a  pump  in  opera- 
tion, and  a  stream  of  varnish  falls  constantly  into  a  shallow  pan, 
or  drained  platform,  on  the  floor.  The  workman  holds  the  chair 
in  this  falling  stream,  turns  it  about  skilfully,  then  throws  it  aside, 
all  varnished  except  the  under  side  of  the  chair  seat,  which  does 
not  need  it.  If  the  chair  were  dipped  this  place  also  would  ab- 
sorb varnish,  which  would  be  a  waste,  and  extravagance  is  a  sin; 
besides,  economies  like  this  make  dividends,  and  keep  the  com- 
pany out  of  the  hands  of  a  receiver.  So  it  is  with  many  other 
things:  there  is  no  use  in  using  a  varnish  which  will  outlast  the 
piece  of  furniture  on  which  it  is  put;  and  the  law  of  the  survival 
of  the  fittest  does  not  apply  to  such  things  as  chairs. 

Furniture  which  does  not  receive  a  high  polish  ought  to  have 
as  elastic  a  coating  as  floor  varnish,  that  is,  one  containing  12 
or  15  gals,  of  oil  to  100  Ibs.  of  resin.  Dark  woods,  such  as  dark 
oak  and  especially  cherry  and  mahogany,  should  receive  a  dark- 
colored  varnish,  which  is  made  from  dark  resin.  These  are  cheaper 
than  pale  resins  of  the  same  kind  and  are  harder  and  better.  Such 


FURNITURE-VARNISHING.  329 

a  varnish  may  therefore  be  of  excellent  quality  and  moderate 
price.  Many  things  will  stand  a  still  more  elastic  varnish,  a  20- 
gallon  for  instance,  such  as  would  be  put  on  interior  woodwork. 
This  becomes  hard  enough  to  rub  in  a  week  or  two,  and  if  a  rubbed 
but  not  polished  finish  is  wanted  it  is  hard  enough.  It  would  be 
too  slow  for  factory  work,  but  it  would  outlast  most  furniture. 

Dark  Varnishes. — The  reason  why  dark  varnishes  are  best  on 
dark  woods  is  that  their  color  enhances  the  beauty  of  the  wood. 
It  is  a  dark  brownish  red,  and  is  transparent.  The  effect  of  a  trans- 
parent color  is  far  more  brilliant  than  that  of  an  opaque  one,  and 
three  or  four  coats  of  such  a  varnish  are  like  a  layer  of  colored 
glass:  it  seems  as  though  one  could  look  down  into  the  wood. 
The  more  varnish  is  applied  the  more  pronounced  is  this  effect. 

Brilliance. — The  larger  the  proportion  of  resin  the  more  bril- 
liant is  the  varnish,  and  the  richer  in  depth  of  color.  This  is  proba- 
bly one  reason  why  varnishes  approaching  the  type  of  carriage 
rubbing-varnish  are  so  much  liked  on  furniture,  in  spite  of  their 
diminished  durability.  The  brilliancy  of  a  varnish,  like  that  of 
a  gem,  depends  on  its  index  of  refraction  of  light,  and  this  sensibly 
increases  with  the  increase  in  the  percentage  of  resin.  Therefore 
in  order  to  get  the  finest  possible  effect,  on  a  piano- case  for  instance, 
it  is  necessary  to  sacrifice  durability  to  an  appreciable  extent.  It 
it  not  exactly  true  that  brilliance  varies  with  percentage  of  resin, 
for  some  resins  are  more  capable  of  imparting  this  effect  than 
others.  An  8-gallon  Manila  varnish  is  less  brilliant  than  an  8-gallon 
Zanzibar.  It  is  a  remarkable  fact  that  the  index  of  refraction  of 
a  varnish  is  higher  than  that  of  its  component  parts.  It  may  thence 
be  inferred  that  this  quality  is  developed  in  making  the  varnish, 
and  that  skill  in  the  operations  will  enable  one  to  make  a  brilliant 
varnish  with  a  larger  proportion  of  oil  than  could  be  used  if  the 
operator  had  less  skill;  and  this  is  true.  A  brilliant  varnish 
ought  then  to  be  made  from  the  materials  which  experience  has 
shown  to  be  best,  and  by  a  skilful  maker,  according  to  a  tried 
.and  satisfactory  as  well  as  a  rational  formula.  There  are  so  many 
variables  that  no  two  varnishes  from  different  sources  are  likely 
to  be  alike;  and  it  is  possible  for  a  maker  to  produce  a  varnish 


330  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

which  is  actually  better  for  a  special  use  than  any  one  else  has 
made.  This  again  is  practically  true;  but  the  art  of  varnish- 
making  is  far  from  stationary,  and  the  best  varnish  to-day  may 
be  superseded  next  year. 

Filling. — It  has  been  said  that  the  finishing  of  furniture  is  much 
like  that  of  carriages.  Of  course  unpainted  furniture,  which  com- 
prises the  greater  part  of  it,  receives  only  priming,  filling,  and 
varnish,  and  the  wood-filler  used  is  never  lead,  but  a  transparent 
filler  such  as  silica.  The  so-called  liquid  wood-fillers  are  also 
used  largely  on  cheap  furniture,  but  nothing  good  can  be  said  of 
them.  The  priming  is  like  all  priming,  done  with  linseed-oil; 
then  the  wood  may  be  filled  with  varnish  directly.  Usually  when 
this  is  done  a  rubbing- varnish  is  used;  or  a  silica  filler,  such  as 
is  used  on  interior  varnished  woodwork  in  houses,  may  be  used. 
This  fills  the  pores  of  the  wood.  Often  a  colored  pigment  is  mixed 
with  it,  the  object  being  to  change  the  color  of  the  wood  by  filling 
the  pores  with  color.  Sometimes  the  color  of  the  whole  of  the 
wood  is  changed,  as  when  birch  is  stained  to  resemble  mahogany. 
This  is  done  with  an  oil- and- pigment  stain,  mixed  in  turpentine, 
and  applied  before  the  priming;  more  rarely  the  wood  is  treated 
with  a  dye.  There  are  a  great  many  dyes  which  are  soluble  in 
alcohol,  and  some  which  dissolve  in  turpentine.  These  are  better 
than  water  dyes,  as  they  do  not  disturb  the  grain  of  the  wood. 
Dyeing  is  necessarily  done  before  anything  else. 

Varnishing. — When  the  surface  is  properly  filled  it  is  sand- 
papered, and  is  then  ready  for  the  varnish.  Any  good  rubbing- 
varnish  will  answer,  but  usually  a  special  rubbing  for  furniture 
is  employed.  The  various  coats  are  applied  and  treated  sub- 
stantially as  on  carriage-work.  The  finishing-coat  is  not  usu- 
ally much  different  from  the  preceding  ones,  because  a  very 
elastic  varnish  is  not  hard  and  firm  enough  for  the  kind  of  use 
furniture  receives.  It  is  flowed  on  with  a  full,  soft  brush,  and 
is  either  left  with  the  gloss,  is  rubbed  to  a  dull  surface,  or  is  pol- 
ished with  rottenstone,  as  has  been  described  in  the  chapter  on 
house-painting. 

Polishing. — It  is  a  rather  common  practice  for  the  workman, 


FURNITURE-VARNISHING.  33  * 

after  he  has  polished  the  surface  as  well  as  he  can  with  rottenstone 
or  some  such  powder,  to  finish  by  rubbing  with  the  palm  of  the 
hand.  The  reader  may  notice  how  the  well-varnished  hand- 
rails in  business  offices  get  polished  by  continual  handling.  This 
is  the  sort  of  finish  obtained  by  hand- polishing,  and  is  the  high- 
est possible  finish;  also  the  most  expensive,  for  it  is  an  almost 
inconceivably  laborious  and  tedious  task.  A  good  workman 
will  sometimes  spend  a  day  on  a  surface  a  foot  square.  It  may 
be  worth  while  to  give  here  a  translation  from  "The  Art  of  the 
Painter,  Gilder  and  Varnisher,"  by  Watin,  published  in  1772. 
This  is  regarded  as  the  oldest  systematic  treatise  of  any  value 
on  the  subject.  Watin's  description  of  the  method  of  polishing 
is  as  follows : 

"To  polish  varnish  is  to  give  it  a  surface  glossy,  clear,  and 
smooth,  which  can  never  be  secured  by  repeated  coats  unless 
we  efface  the  little  inequalities  which  occur.  To  do  this  we  use 
pumice  and  tripoli.  Pumice  is  a  stone  which  has  become  light 
and  porous  because  it  has  been  calcined  by  subterranean  fires, 
and  thrown  by  eruptions  into  the  sea,  where  it  is  found  floating. 
Without  regarding  its  form,  there  are  many  sorts,  various  weights,, 
some  gray,  some  white.  Those  most  esteemed  are  the  coarsest, 
the  lightest,  and  the  purest.  It  ought  to  be  porous,  spongy,  with 
a  salt  taste.  It  is  brought  from  Sicily,  opposite  Mt.  Vesuvius, 
from  which  it  is  thrown  out. 

"When  we  wish  to  use  it  in  powder,  it  is  necessary  that  this 
powder  should  be  impalpable,  so  that  it  will  not  scratch  the  work 
we  are  polishing. 

"Tripoli  is  a  light  stone,  pale  in  color,  inclining  slightly  to 
red,  which  is  brought  from  many  localities,  in  Bretagne,  Auvergne, 
and  Italy.  It  is  thought  from  the  lightness  of  this  stone  that  it 
has  been  calcined  by  subterranean  fires.  We  find  two  sorts  in 
France.  The  first  and  the  best  is  that  which  is  brought  from  a 
mountain  near  Rennes  in  Bretagne.  They  find  it  in  beds  about 
a  foot  thick.  It  is  used  by  painters,  lapidaries,  goldsmiths,  and 
coppersmiths  to  brighten  and  polish  their  work.  The  second,  and 
less  valued,  comes  from  Auvergne,  near  Riom.  It  will  not  serve 


33 2  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

for  our  uses,  but  it  is  used  in  houses  to  clean  and  brighten  the 
kitchen  utensils. 

"To  polish  an  oleo- resinous  varnish,  when  the  last  coat  is 
thoroughly  dry,  proceed  as  follows:  Pulverize,  grind,  and  sift 
some  pumice,  so  that  you  may  suspend  it  in  water,  and  with  this 
saturate  a  piece  of  serge  and  polish  lightly  and  uniformly,  not 
more  in  one  place  than  another,  so  as  to  avoid  spoiling  the  founda- 
tion. Then  rub  with  a  bit  of  clean  cloth  moistened  with  olive- 
oil  and  with  tripoli  in  very  fine  powder.  Many  workmen  use  for 
this  pieces  of  hats;  but  this  always  tarnishes  the  work  and  may 
injure  the  foundation.  Wipe  it  off  with  a  soft  cloth  in  such  a 
way  that  it  shall  be  bright  and  show  no  streaks.  When  it  is 
dry,  polish  it  with  starch-powder  or  whiting1  by  rubbing  with 
the  palm  of  the  hand,  and  wiping  it  off  with  a  linen  cloth.  This 
last  is  the  operation  of  polishing.  Spirit-of-wine  varnishes  may, 
when  they  are  very  dry,  be  polished  in  the  same  way,  only  omit- 
ting the  use  of  pumice." 

"  Vernis-Martin." — Watin,  as  has  been  said,  was  the  first 
writer  on  the  subject.  He  was  an  artist  and  a  man  of  science; 
but  long  before  his  book  was  written,  Robert  Martin  had  estab- 
lished a  great  reputation,  which  has  lasted  until,  the  present  time, 
as  a  maker  and  especially  as  a  varnisher  of  fine  furniture.  There 
were  three  brothers  of  the  name,  one  of  whom,  William,  estab- 
lished himself  as  a  varnisher  at  Rochefort,  but  Robert,  whom 
Watin  calls  "the  famous  Martin,"  was  at  Paris.  Watin  speaks 
of  "my  profound  veneration  for  all  who  carry  the  name  of  Martin, 
our  masters  in  the  art  of  varnish,"  and  describes  the  varnish 
made  by  melting  copal,  adding  linseed- oil  and  turpentine,  and 
says:  "It  is  thus  that  the  famous  Martin  made  his  beautiful 
pale  oleo-resinous  varnishes,  which  gave  him  so  much  reputa- 
tion." It  is  worthy  of  remark  that  these  brothers  were  carriage- 
builders,  and  that  their  skill  as  finishers,  at  a  time  when  every 
shop  made  its  own  varnish,  led  them  into  the  more  lucrative 
business  of  fine  furniture,  in  which  they  became  unrivalled. 
The  later  editions  of  Chambers' s  Encyclopaedia  were  published  at 
the  time  when  Martin  was  producing  his  work.  From  this  source 


FURNITURE-VARNISHING.  333 

we  learn  that  Martin  used  an  oleo-resinous  varnish,  a  mixture 
of  one- third  amber  and  two- thirds  copal,  with  enough  linseed- oil 
to  make,  in  our  nomenclature,  about  a  i3-gallon  varnish.  Diderot 
and  D'Alembert,  in  their  Encyclopaedia,  written  in  Paris  about 
the  same  time,  give  the  same,  only  with  a  larger  proportion  of  oil. 
Martin's  process  is  thus  described  by  Chambers : 

"The  article  to  be  varnished,  after  having  been  varnished 
smoothly,  and  dried  in  the  intervals,  half  a  dozen  times,  and 
suffered  to  dry  thoroughly,  must  be  rubbed  with  a  wet,  coarse 
rag,  dipped  in  pumice-stone  powdered  and  sifted,  till  the  streaks 
of  the  brush  and  all  blemishes  are  removed.  When  it  is  per- 
fectly smoothed,  washed,  and  dried,  the  coats  of  varnish  are  to 
be  repeated,  for  ten  or  twelve  times,  till  there  be  a  sufficient 
body.  After  having  again  used  the  pumice-stone,  and  washed 
it  off  as  before,  let  it  be  rubbed  with  fine  emery  till  the  surface 
becomes  even  and  smooth  as  glass;  then  with  powder  of  fine 
rottenstone,  till  by  passing  the  palm  of  the  hand  two  or  three 
times  over  the  same  place,  you  discover  a  gloss  equal  to  that 
of  glass;  having  dried  it  clean,  dip  a  rag,  or  a  piece  of  flannel, 
in  sweet- oil,  and  rub  the  surface  a  few  times  over,  and  clear  it 
off  with  fine  dry  powder,  flour,  or  the  hand;  and  a  piece  of  fine 
flannel,  dipped  in  flour,  and  rubbed  over  it,  when  cleared  of  oil, 
will  give  it  an  excellent  lustre.  Between  every  coat  of  varnish  it 
will  be  advisable,  if  the  subject  admits  of  it,  to  set  it  in  a  warm 
oven,  or  to  heat  the  varnished  pieces  by  stoves." 

Durability  of  Good  Work. — That  was  the  way  they  finished 
furniture  in  the  year  1750;  that  is  the  finish  called  "vernis- 
Martin";  and  that  finish  is  on  that  same  furniture  to-day.  Do 
not  say  that  varnish  is  necessarily  a  short-lived  commodity. 
Remember  what  Xenophon  said  about  the  horse's  feet,  and 
the  counsel  of  the  prophet  Isaiah. 

Ancient  Practice. — But  Martin  was  not  the  originator  of  the 
method  of  polishing  which  he  practised.  It  is  mentioned  by  the 
monk  Theophilus  in  the  tenth  or  eleventh  century,  who  says 
that  varnish  is  polished  with  the  hand.  Going  further  back 
we  find  that  Vitruvius,  in  the  first  century  B.C.,  says  that  wain- 


334  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

scotting  is  varnished,  then  rubbed  and  polished.  "Subigendiet 
poliendi,"  are  his  words  (book  vn,  chap.  4),  and  he  also  says 
that  this  rubbing  was  done  with  a  powder  like  ochre  interposed. 
Elsewhere  the  same  author  uses,  with  the  same  meaning,  the 
words  "subactum  et  bene  fricatum."  Cicero  says  that  Apelles 
polished  his  paintings,  but  possibly  this  only  refers  to  his  skill  in 
varnishing  them,  of  which  mention  has  already  been  made;  but 
Nicias,  who  was  a  painter  of  the  fourth  century  B.C.,  is  expressly 
said  by  Pliny  to  have  "put  his  hand  to"  his  work,  and  to  have 
taken  "much  care  in  rubbing"  it  (book  xxxv,  chap.  28).  Thus 
we  have  what  seems  to  be  a  clear  case  of  handing  down  a  tech- 
nical method  for  twenty- three  hundred  years. 

Refinishing  Old  Furniture. — To  refinish  old  furniture  it  is 
desirable  to  remove  first  the  old  varnish,  not  because  old  varnish 
is  harmful  as  such,  but  because  we  know  nothing  about  it,  and 
if  we  are  to  spend  a  large  amount  of  work  on  an  article  we  should 
be  sure  about  the  foundation.  The  old  varnish  may  be  removed 
by  scraping  it  with  steel  scrapers  or  with  broken  glass,  then 
scouring  it  with  sandpaper;  or  else  we  may  begin  with  a  paint- 
remover  and  carefully  take  off  all  the  varnish,  and  immediately 
wash  it  off  with  benzine.  This  part  of  the  work  should  be  done 
out  of  doors,  for  fear  of  fire.  Then  apply  a  thin  varnish.  This 
maybe  from  a  15-  to  a  2o-gallon  varnish  (gallons  of  linseed-oil  per 
hundred  pounds  of  resin),  and  should  be  of  good,  hard  resins, 
part  Kauri  and  part  some  hard  African  resin.  This  should  be 
thinned  with  turpentine.  Starting  with  a  varnish  of  ordinary 
body  it  is  well  to  add  from  an  eighth  to  a  fifth  its  volume  of  tur- 
pentine, and  this  mixture,  after  being  well  shaken,  should  stand 
in  a  warm  room  at  least  two  or  three  months.  This  may  be  regarded 
as  essential,  for  if  used  at  once,  although  the  original  varnish  may 
(and  must)  have  been  well  aged,  the  mixture  will  behave  in 
some  ways  like  a  fresh  varnish.  This  thin  varnish  is  carefully 
brushed  on  in  thin  coats,  plenty  of  time  being  given  for  each  to 
dry  and  become  hard,  at  least  two  weeks  between  coats,  unless 
there  is  a  hot  room,  with  a  temperature  of  at  least  130°  F.,  in 
which  it  may  be  set;  then  the  time  will  be  reduced  according  to 


FURNITURE-VARNISHING.  335 

the  temperature.  Each  coat  when  perfectly  dry  should  be 
rubbed,  at  first  with  very  fine  sandpaper,  but  after  enough  coats 
have  been  put  on  to  be  sure  that  none  of  the  water  used  can 
reach  the  wood,  powdered  pumice  and  water  may  be  used  spar- 
ingly. The  surface  should  then  be  washed  with  clean  water,  using 
a  clean  brush  to  get  it  into  corners  and  depressions,  and  made 
perfectly  dry  and  warm  before  the  following  coat  of  varnish  is 
applied.  Of  course  all  the  precautions  against  dirt,  dust,  and 
dampness  which  can  be  thought  of  must  be  used,  and  in  par- 
ticular the  brushes  must  be  treated  with  care.  Only  as  much 
varnish  as  is  to  be  used  at  one  time  should  be  taken  from  the 
can,  which  should  be  then  immediately  stoppered.  Any  varnish 
which  has  been  taken  out  should  not  be  put  back,  for  fear  of 
getting  dirt  in  the  can,  a  thing  which  would  almost  certainly 
happen.  The  very  thin  coats  secured  in  this  way  will  make  a 
body  of  varnish  which  is  much  more  uniform  and  homogeneous 
than  if  thicker  varnish  were  used;  and  the  reader  will  easily 
understand  that  these  are  to  be  repeated  until  a  thickness  has 
been  secured  great  enough  to  be  rubbed  to  an  even,  level  surface. 
Then  repeat  the  treatment  until  enough  varnish  has  been  applied 
to  get  the  desired  lustre;  after  which  it  should  be  rubbed  and 
polished.  Always  remember  the  intermediate  light  rubbing 
between  coats,  to  get  a  proper  adhesion  of  the  successive  layers. 
Flow  on  the  varnish  lightly,  but  smoothly  and  rapidly,  with  a 
fine  new  brush,  and  do  not  brush  it  too  much  or  it  will  be  full  of 
bubbles,  and  if  you  brush  it  after  it  has  begun  to  set  it  will  roll 
up;  then  all  that  can  be  done  is  to  get  it  off  as  quickly  as  possible 
with  a  brush  wet  with  spirit  of  turpentine,  and  immediately 
revarnish ;  but  this  should  never  occur.  The  successful  varnisher 
works  rapidly,  with  a  steady  hand,  and  is  not  afraid  of  the  varnish ; 
but  he  does  not  use  too  much.  The  amateur  will  do  well  to  go 
from  time  to  time  and  watch  some  good  workman.  The  art,  like 
all  arts,  is  learned  from  observation  and  practice  combined. 
The  amateur  should  practise  by  preparing  and  finishing  experi- 
mental panels.  For  this  purpose  he  can  buy,  in  the  city  shops, 


336  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

cake-boards  of  a  convenient  size,  dry  and  smooth,  for  a  trifling 
sum;   nothing  can  be  better  for  practice. 

Violin  Varnish. — Occasionally  a  mechanic,  especially  an 
amateur  mechanic,  is  also  an  amateur  musician;  a  trouble- 
breeding  combination,  which  sometimes  leads  to  the  construction 
of  violins.  There  is  a  belief,  so  universal  that  it  is  probably  true, 
as  it  is  inherently  reasonable,  among  violinists  that  the  varnish 
on  a  violin  affects  its  musical  quality.  It  is  therefore  desirable  to 
use  a  suitable  varnish.  Books  of  recipes  usually  advise  using  a 
spirit  varnish,  which  may  be  colored  to  suit;  but  the  writer  does 
riot  believe  such  varnishes  were  ever  used  by  the  great  violin- 
makers.  From  the  nature  of  the  case  it  is  difficult  to  get  samples 
for  examination,  but  one  can  occasionally  have  an  opportunity 
to  look  carefully  at  an  old  violin,  and  these  always  appear  to  have 
been  coated  with  an  oleo- resinous  varnish.  A  varnish  expert 
has  shown  me  an  old  violin,  about  two  hundred  years  old,  very 
valuable,  which  had  in  one  place  what  appeared  to  be  the  original 
varnish  in  a  layer  of  considerable  thickness;  on  this  surface  a 
long- continued  pressure  with  the  finger-nails  made  a  sensible 
depression,  which  afterward  disappeared.  If  this  varnish  was 
old,  and  it  certainly  was,  it  must  have  been  made  with  at  least 
35  gals,  of  oil  to  100  Ibs.  of  resin;  and  such  a  varnish  would 
probably  last  two  or  three  hundred  years,  possibly  several  times 
that,  under  the  conditions  in  which  a  valuable  violin  is  kept. 
Such  a  varnish  could  have  had  little,  probably  not  any,  drier  in  it. 
The  violin  was  varnished,  put  in  a  dry  dust-proof  cupboard,  and 
left  for  some  months  before  the  next  coat  was  applied.  The  time 
was  of  no  consequence,  since  it  is  generally  believed  that  a  violin 
must  be  kept  a  year  or  two  after  it  is  made  before  it  is  ready  for 
use,  and  such  a  varnish  would  by  its  perfect  elasticity  not  inter- 
fere with  the  normal  vibrations  of  the  wood;  whereas  the  writer 
is  told  by  experts  that  spirit  varnishes,  which  produce  simply  a 
layer  of  dry  resin  on  and  in  the  surface,  make  the  tone  of  the 
instrument  harsh.  As  to  color,  in  the  first  place  the  old  instru- 
ment-makers made  amber  varnish.  We  are  accustomed  to  think 
of  amber  as  a  pale  golden-yellow  resin,  but  the  sorts  used  in 


FURNITURE-VARNISHING.  337 

varnish-making  are  dark  brownish  red,  and  in  melting  all  resins 
darken  very  much;  so  that  amber  varnish  is  very  dark  in  color, 
so  much  so  that  it  is  unsalable  for  any  ordinary  work.  It  might 
have  had  color  enough  to  suit  the  makers;  and  it  is  a  beautiful, 
rich,  deep  color.  Then  comes  in  the  matter  of  age.  No  one  can 
look  at  one  of  these  old  instruments  without  feeling  that  the  tone 
of  the  color  is  due  to  age;  the  long- continued  darkening  action 
of  light  can  never  be  imitated  by  a  dye.  There  is  besides  evi- 
dence of  a  historical  sort.  The  great  violin-makers  lived  at  the 
time  when  the  great  masters  of  painting  were  executing  their 
works  in  amber  and  copal  varnish,  and  must  have  known  of  the 
value  of  these  preparations.  Eastlake  describes  a  manuscript  in 
the  British  Museum,  dated  1620,  written  by  De  Mayerne,  who 
was  chief  physician  to  the  King  of  England,  and  who  is  well 
known  to  have  been  a  man  of  great  and  varied  technical  learning, 
De  Mayerne  describes  the  making  of  varnish  from  amber  and 
linseed-oil,  as  it  was  experimentally  taught  him  by  M.  Laniere, 
who  learned  it  from  the  daughter  of  the  eminent  Florentine 
painter  Gentileschi,  whose  paints  were  made  with  this  varnish 
as  the  vehicle.  This  was  called  the  amber  varnish  of  Venice.  It 
was  at  first  turbid  but  could  be  settled  by  mixing  brick-dust  with 
it;  and  De  Mayerne  says  it  was  commonly  used  for  lutes  and 
other  musical  instruments.  Mrs.  Merrifield  and  others  have  also 
collected  evidence  showing  that  although  turpentine  varnishes 
were  unquestionably  in  common  use,  yet  all  the  makers  of  high- 
priced  wares  used  also  varnish  made  of  amber  and  oil.  There 
is  considerable  of  this  sort  of  evidence,  and  when  taken  in  con- 
nection with  the  fact,  which  probably  most  experts  would  agree 
upon,  that  the  varnish  on  these  old  instruments  appears  to  be 
oleo- resinous,  and  the  further  unquestioned  fact  that  no  spirit 
varnish  of  such  qualities  is  known  to  us  either  experimentally  or 
by  tradition,  it  seems  that  we  are  warranted  in  believing  that 
such  varnishes  as  have  been  described  were  the  ones  used  by 
the  more  important  makers  of  violins;  and  that  we  are  to  advise 
the  use  of  a  carriage  finishing-varnish  unless  one  darker  and 
more  elastic  can  be  had.  Probably  most  varnish-makers  can 


338  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

supply  a  25-  to  3o-gallon  dark  varnish,  although  they  do  not  ordi- 
narily sell  it  unmixed  with  a  harder  one.  If  the  writer  were  to 
make  a  special  varnish  for  this  use  it  would  be  a  straight  amber 
varnish,  with  35  or  40  gals,  of  raw  linseed-oil. 

To  revert  for  a  moment  to  the  subject  of  furniture,  it  should 
be  said  that  the  makers  of  the  better  class  of  these  goods  use  very 
good  varnish,  not  unfrequently  thinned  with  benzine  instead  of 
turpentine,  for  cheapness,  which  accounts  for  brush-marks  often 
seen  on  articles  which  are  left  with  the  natural  gloss,  and  the 
finish  is  surprisingly  good  when  we  consider  the  price  received  for 
the  finished  furniture.  Such  a  finish  cannot  be  produced  if  a  very 
poor  varnish  is  used. 

Brushes. — A  few  words  may  be  here  added  concerning  the 
proper  care  of  varnish-  and  paint-brushes.  If  these  are  left  to 
dry  with  the  varnish  or  paint  in  them  they  are  spoiled;  they  are 
to  be  cleaned  thoroughly,  or  else  kept  in  some  liquid  which  will 
preserve  them.  As  to  what  this  liquid  should  be  there  is  differ- 
ence of  opinion;  some  put  the  brushes  in  water,  some  in  linseed- 
oil,  some  in  varnish,  but  probably  the  most  use  turpentine.  What- 
ever liquid  is  used  the  treatment  is  the  same;  the  brush  is  not 
immersed,  handle  and  all,  but  is  suspended  in  a  vertical  position, 
dipping  just  far  enough  in  the  liquid  so  that  it  comes,  up  to  where 
the  bristles  (or  hair)  disappear  in  the  binding  which  unites  them 
to  the  handle.  The  brush  should  not  rest  on  the  point  of  the 
bristles,  as  this  will  injure  its  shape  and,  in  time,  its  elasticity, 
but  should  be  hung  up  by  the  handle.  Tin  boxes  for  this  pur- 
pose, called  brush  safes  or  keepers,  are  for  sale  by  the  dealers. 
They  are  tightly  covered  to  prevent  evaporation  and  to  keep  out 
dust,  and  have  hooks  or  other  attachments  for  suspending  the 
brushes.  A  simple  and  perfectly  good  keeper  for  one  or  perhaps 
two  brushes  may  be  made  by  soldering  to  a  tin  cup  (one  without 
a  handle),  or  a  small  empty  can  with  the  top  removed,  a  wire;  this 
wire  stands  vertically  when  the  cup  is  on  its  bottom,  and  reaches 
up  about  as  high  as  the  length  of  the  brush,  handle  and  all.  Then 
bend  this  wire  at  right  angles,  say  2  ins.  below  the  top,  so  that  the 
bent  part  may  overhang  the  cup.  Make  a  good-sized  hole  in  the 


FURNITURE-VARNISHING.  339 

handle  of  the  brush  at  a  suitable  place,  so  that  when  it  is  hung  on 
the  bent  part  of  the  wire  it  will  hang  in  the  cup,  the  bristles  just 
clearing  the  bottom.  Then  fill  the  cup  with  turpentine  or  oil,  so 
as  to  wet  the  bristles;  and  to  keep  out  dust  the  whole  thing  may 
be  lowered  into  a  glass  fruit- jar  and  the  top  screwed  down.  In 
order  to  more  easily  lower  the  apparatus  into  and  draw  it  out  of 
the  jar,  it  is  common  to  solder  a  second  piece  of  wire  to  the  first, 
projecting  above  it,  for  a  handle.  This  is  a  cheap  and  satisfac- 
tory arrangement  and  illustrates  the  principles  on  which  all  brush 
safes  should  be  constructed.  Brushes  used  in  spirit  varnishes 
should  not  be  put  in  water,  but  in  alcohol,  and  if  a  brush  is  to  be 
put  away  for  a  long  time  it  may  be  washed  out  with  turpentine  or 
benzine  (a  spirit- varnish  brush  in  alcohol,  usually  wood- alcohol), 
and  when  as  clean  as  it  can  be  conveniently  made  in  this  way  it 
may  be  washed  out  with  soap  and  water,  very  thoroughly  rinsed 
with  clean  water,  and  dried  as  quickly  as  possible.  Each  brush 
should  be  separately  wrapped  in  clean  paper,  and  kept  in  a  dry 
place. 

As  to  choice  of  brushes,  that  is  too  large  a  subject  to  be  treated 
here.  The  student  will  do  well  to  write  to  some  of  the  brush-makers 
for  an  illustrated  catalogue,  and  by  studying  that,  get  some  idea 
of  the  sorts  and  shapes  of  brushes  in  use,  after  which  he  may  ask 
advice  of  the  professional  painter  who  is  doing  the  sort  of  work 
which  interests  the  amateur.  There  is  considerable  room  for  the 
personal  equation;  but  all  agree  that  good  work  cannot  be  done 
without  good  brushes,  and  the  best  brushes  quickly  cease  to  be 
good  if  not  kept  clean. 


CHAPTER   XXII. 
CONCLUSION. 

IT  is  probable  that  many  of  the  readers  of  this  book  will  feel 
a  reasonable  interest  in  knowing  something  about  the  former  prac- 
tice of  those  who  made  and  used  the  products  which  have  been 
described.  Many  references  of  this  sort  have  been  incidentally 
made.  Our  knowledge  of  former  applications  of  the  art  is  not 
continuous,  nor  even  connected,  but  the  total  amount  is  consider- 
able; more  concerning  its  decorative  and  artistic  branches  than 
of  the  technical  side.  Pliny's  Natural  History  is  the  great  foun- 
tain of  knowledge  of  such  things;  much  may  be  learned  from 
Vitruvius  and  Dioscorides.  These  writers  had  access  to  writings 
and  other  sources  of  information  now  lost,  and  no  doubt  they  give 
reasonably  correct  accounts  of  earlier  practice,  and  there  is  no 
reason  to  doubt  their  accuracy  when  they  describe  their  own 
times.  Aside  from  these  writers  we  may  only  pick  up  occasional 
bits  from  the  more  ancient  writers,  introduced  incidentally,  and 
to  illustrate  some  other  matter.  Thus,  in  Xenophon's  "  Econo- 
mist" one  of  the  speakers  tells  that  his  wife  was  at  one  time  in 
the  habit  of  rubbing  white  lead  into  her  skin  to  make  her  face 
look  white,  and  then  dyeing  her  cheeks  and  lips  with  alkanet  to 
make  them  red,  and  adds  that  she  also  wore  high-heeled  shoes 
to  make  herself  tall;  which  shows  that  white  lead  has  been  properly 
valued  for  twenty- three  centuries  at  least.  It  is  pleasing  to  be  able 
to  add  that  in  this  particular  case  the  husband  assured  his  wife 
that  he  would  love  her  just  the  same  if  she  washed  her  face  and 
put  on  comfortable  foot-gear;  and  she,  being  recently  married, 
and  knowing  that  she.  was  young  and  pretty  anyway,  did  as  he 
advised,  and  of  course  had  continued  to  do  so  up  to  the  time  when 

340 


CONCLUSION.  341 

he  told  of  it.  It  is  unnecessary  to  say  that  the  use  of  white  lead 
as  a  cosmetic  did  not  cease;  and  we  find  in  Cennim's  time  that 
not  only  was  paint  used,  but  that  one  of  the  branches  of  the  artist- 
painter's  work  was  to  paint,  and  not  only  to  paint  but  to  varnish, 
people's  faces.  Hear  him : 

"  Sometimes,  in  the  course  of  your  practice,  you  will  be  obliged 
to  paint  flesh,  especially  the  faces  of  men  and  women.  You  may 
temper  your  colors  with  yolk  of  egg;  or,  if  you  desire  to  make  them 
more  brilliant,  with  oil,  or  with  liquid  varnish,  which  is  the  most 
powerful  of  temperas.  But  should  you  wish  to  remove  the  colors 
or  tempera  from  the  face,  take  the  yolk  of  an  egg,  and  rub  a  little 
of  it  at  a  time  on  the  face  with  the  hand.  Then  take  clean  water 
that  has  been  boiled  on  bran,  and  wash  the  part  with  it;  then  take 
more  of  the  yolk  of  egg,  and  rub  it  again  on  the  face,  and  again 
wash  it  with  the  warm  water.  Do  this  many  times  until  the  color 
be  removed  from  the  face."  (Chap.  161.) 

In  another  chapter  he  expresses  his  disapprobation  of  the  prac- 
tice, saying: 

"It  sometimes  happens  that  young  ladies,  especially  those  of 
Florence,  endeavor  to  heighten  their  beauty  by  the  application  of 
colors  and  medicated  waters  to  their  skin.  But  I  advise  you,  that 
if  you  desire  to  preserve  your  complexion  for  a  long  period,  to  wash 
yourselves  with  water  from  fountains,  rivers,  or  wells;  and  I  warn 
you,  that  if  you  use  cosmetics,  your  face  will  soon  become  withered, 
your  teeth  black,  and  you  will  become  old  before  the  natural  course 
of  time,  and  be  the  ugliest  object  possible. " 

Between  Cennini,  who  described  the  art  as  practised  in  the 
fourteenth  century,  and  the  classical  writers  there  are  many 
authorities  of  more  or  less  importance.  The  best  known  is 
the  monk  Theophilus,  a  varnish  formula  from  whom  has  already 
been  given;  but  there  are  others,  both  earlier  and  later.  The- 
ophilus is  especially  eminent  for  two  reasons:  his  work  is  a  sys- 
tematic treatise  on  various  arts,  giving  simple  and  intelligible 
working  directions;  and  there  exist  several  manuscript  copies, 
showing  that  it  was  widely  known.  This  is  also  evident  by  the 
extracts  from  it  found  in  later  writers.  Among  the  earlier  writers 


342  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

is  Eraclius,  who  is  by  some  authorities  assigned  to  the  seventh 
century.  He  was  at  any  rate  prior  to  Theophilus,  as  has  else- 
where been  mentioned;  his  style  indicates  an  early  date.  The 
formula  he  gives  for  refining  linseed-oil  has  already  been  given. 
It  is  noteworthy  that  he  says  this  refined  oil  was  used  for  mixing 
with  pigments,  showing  that  oil  painting  was  practised  in  his 
time.  The  carriage-painter  will  be  interested  to  read  how  Erac- 
lius recommends  preparing  the  surface  of  wood,  particularly  his 
way  of  making  rough-stuff: 

"First  plane  the  wood  perfectly,  rubbing  the  surface  at  last 
with  shave-grass.  If  the  wood  is  of  such  a  nature  that  its  rough- 
ness cannot  be  reduced,  grind  dry  white  lead  on  a  slab,  but  do  not 
grind  it  so  finely  as  if  you  were  to  paint  with  it.  Then  melt 
some  wax  on  the  fire;  add  finely  pulverized  tile  and  the  lead 
already  ground;  mix  together,  stirring  with  a  small  stick,  and 
suffer  the  composition  to  cool.  Afterwards,  with  a  hot  iron, 
melt  it  into  the  cavities  until  they  are  even,  and  then  with  a  knife 
scrape  away  inequalities;  and  should  you  be  in  doubt  whether 
it  is  advisable  to  mix  white  lead  with  wax,  know  that  the  more 
you  mix  the  harder  it  will  be.  The  surface  being  smooth,  take 
more  white,  finely  ground  with  oil,  and  spread  it  thinly,  with  a 
brush  adapted  for  the  purposes,  wherever  you  wish  to  paint; 
then  let  it  dry  in  the  sun.  When  dry  add  another  coat  of  color 
as  before,  rather  stiffer,  but  not  so  stiff  as  to  make  it  necessary 
to  load  the  surface,  only  let  it  be  less  oily  than  before,  for  great 
care  is  to  be  taken  never  to  let  the  second  coat  be  more  fat  than 
the  first.  If  it  were  so,  and  at  the  same  time  more  abundant,  the 
surface  would  become  wrinkled  in  drying." 

This  is  a  remarkable  passage,  when  we  consider  that  it  was 
written  a  thousand,  and  probably  twelve  hundred  years  ago. 
The  remark  that  lead  to  be  used  as  a  filler  should  not  be  too 
fine  is  evidence  of  great  discernment;  and  the  use  of  powdered 
tile  for  the  necessary  grit  in  the  rough-stuff  is  excellent.  Wax 
was  used  instead  of  varnish;  probably  wax  may  make  a  good 
vehicle,  but  more  difficult  to  apply  than  the  other.  It  was  mixed 
with  a  stick;  this  was  a  common  precaution  to  avoid  getting  a 


CONCLUSION.  343 

trace  of  Iron  into  the  compound.  Compare  Cennini's  use  of  a 
wooden  spatula  for  scraping  the  porphyry  slab  on  which  colors 
are  ground.  Then  note  that  the  surface  was  levelled  and  cleaned 
with  a  knife,  exactly  as  "knifing-lead"  is  used  on  wagon-bodies 
to-day.  Shave-grass  is  the  scouring-rush,  a  species  of  Equise- 
tum,  and  was  used  as  we  now  use  sandpaper,  down  to  quite  recent 
times.  It  is  full  of  spiculae  of  silex  and  is  a  perfectly  good  sub- 
stitute for  sandpaper,  only  less  rapid  in  its  action.  Evidently 
the  man  who  wrote  this  account  was  skilled  in  the  art,  and  the 
art  itself  was  not  of  a  crude  sort.  Cennini,  who  wrote  six  hun- 
dred years  later,  gives  directions  essentially  similar.  His  details 
are  scattered  through  the  book  and  are  not  readily  copied  as  a 
whole.  He  recommends  the  use  of  bone-dust  as  an  ingredient  of  a 
filler.  He  says: 

"For  this  purpose  take  the  bones  of  the  ribs  and  wings  of 
fowls  or  capons,  and  the  older  they  are  the  better.  When  you 
find  them  under  the  table,  put  them  into  the  fire,  and  when  you 
see  that  they  are  become  whiter  than  ashes  take  them  out  and 
grind  them  well  on  a  porphyry  slab,  and  keep  the  powder  for 
use."  The  translator  remarks  that  this  rather  singular  allusion 
to  the  manner  of  the  times  shows  that  the  practice  of  picking 
bones,  and  throwing  them  under  the  table,  was  universal.  East- 
lake  says  that  as  late  as  the  middle  of  the  nineteenth  century 
Spanish  painters  saved  chicken-bones  from  the  table  for  a  similar 
purpose.  Cennini  says  that  some  boards  which  are  to  be  painted 
are  "primed  with  chalk  mixed  with  white  lead  and  oil,  using  the 
bone-dust  as  before  mentioned."  Parchment  was  also  filled  in 
this  way.  He  also  describes  a  filler  made  of  gypsum;  but  what 
is  more  interesting,  he  describes  the  use  of  a  guide-coat,  by  sifting 
powdered  charcoal  over  the  surface  of  the  filler,  laying  it  smoothly 
with  a  feather;  when  the  rubbing  is  afterward  completed  it  will 
be  seen  that  this  guide-coat  has  disappeared.  He  says  of  the 
surface  of  the  wood:  "Let  it  be  made  quite  smooth;  if  it  be  de- 
faced with  knots,  or  if  it  be  greasy,  you  must  cut  it  away  as  far 
as  the  grease  extends,  for  there  is  no  other  remedy.  The  wood 
must  be  very  dry;  and  if  it  be  such  a  piece  that  you  can  boil  in 


344  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

a  cauldron  of  clean  water,  after  the  boiling  it  will  never  split.  Let 
us  now  return  to  the  knots,  or  any  other  defect  in  the  smooth- 
ness of  the  panel.  Take  some  glue,  and  about  a  glassful  of  clean 
water,  melt  and  boil  two  pieces  in  a  pipkin  free  from  grease; 
then  put  in  a  porringer  some  sawdust,  and  knead  it  into  the  glue; 
fill  up  the  defects  or  knots  with  a  wooden  spatula,  and  let  them 
remain.  Then  scrape  them,  with  the  point  of  a  knife,  till  they  are 
level  with  the  rest  of  the  panel.  Examine  if  there  be  any  nail, 
or  other  thing,  that  renders  the  panel  uneven,  and  knock  it  into 
the  panel;  then  provide  some  pieces  of  tin-plate,  like  small  coins, 
and  cover  the  iron  with  them.  And  this  is  done  that  the  rust  of 
the  iron  may  not  rise  through  the  ground.  The  surface  of  the 
panel  cannot  be  too  smooth."  (Chap.  113.)  Note  the  use  of 
the  wooden  spatula,  to  avoid  marring  the  wood,  as  we  now  use 
one  in  puttying  interior  woodwork. 

The  same  writer  gives  directions  for  boiling  oil,  but  none  for 
making  varnish ;  but  his  description  of  varnishing  pictures  appears 
to  be  the  earliest  complete  account  of  the  operation,  and  for  that 
reason  deserves  reproduction:  "You  must  know  that  the  longer 
you  delay  varnishing  your  picture  after  it  is  painted,  the  better  it 
will  be.  And  I  speak  truth  when  I  say,  that  if  you  would  delay 
for  several  years,  or  at  least  for  one  year,  your  work  will  remain 
much  fresher.  The  reason  for  this  is,  that  the  coloring  naturally 
acquires  the  same  condition  as  the  gold,  which  shuns  a  mixture 
with  other  metals;  so  the  colors  when  mixed  with  their  proper 
tempera  dislike  the  addition  of  other  mixtures  to  their  own  tem- 
pera. Varnish  is  a  strong  liquor,  which  brings  out  the  color, 
will  have  everything  subservient  to  it,  and  destroys  every  other 
tempera.  And  suddenly,  as  you  spread  it  over  the  picture,  the 
colors  lose  their  natural  strength,  and  are  powerfully  acted  on 
by  the  varnish,  and  their  own  tempera  has  no  longer  any  effect 
on  them.  It  is  therefore  proper  to  delay  varnishing  as  long  as 
you  can;  for  if  you  varnish  after  the  tempera  has  had  the  proper 
effect  on  the  colors,  they  will  afterwards  become  more  fresh 
and  beautiful,  and  the  greens  will  never  change.  Then  take 
liquid  and  clear  varnish,  the  clearest  you  can  obtain;  place  your 


CONCLUSION.  345 

picture  in  the  sun,  wipe  it  as  clean  as  you  can  from  dust  and  dirt 
of  every  kind.  And  varnish  it  when  there  is  no  wind,  because 
the  dust  is  subtle  and  penetrating;  and  every  time  that  the  wind 
blows  over  your  picture  you  will  have  more  difficulty  in  making 
it  clean.  It  will  be  best  to  varnish  it  in  a  green  meadow  by  the 
sea- side,  that  the  dust  may  not  injure  it.  When  you  have  warmed 
the  picture  and  the  varnish  also  in  the  sun,  place  the  picture  level 
and  with  your  hands  spread  the  varnish  well  over  the  surface. 
But  be  careful  not  to  touch  the  gold  with  it,  for  varnish  and 
other  liquors  injure  it.  If  you  do  not  choose  to  spread  the  var- 
nish with  your  hand,  dip  a  piece  of  clean  sponge  into  the  varnish 
and  spread  it  over  the  picture  in  the  usual  manner.  If  you 
wish  the  varnish  to  dry  without  sun,  boil  it  well  first  and  the 
picture  will  be  much  better  for  not  being  too  much  exposed  to 
the  sun."  (Chap.  155.) 

It  may  be  well  to  repeat  that  the  word  tempera  means  the 
liquid,  or  vehicle,  with  which  the  colors  are  mixed;  modern 
painters  often  use  it  as  though  it  meant  only  a  vehicle  for  water- 
colors,  but  there  is  no  doubt  that  the  word  was  commonly  used 
exactly  as  we  use  the  word  vehicle.  In  chapter  161,  already  quoted, 
Cennini  says:  "You  may  temper  your  colors  with  yolk  of  egg; 
or  if  you  desire  to  make  them  more  brilliant,  with  oil,  or  with 
liquid  varnish,  which  is  the  most  powerful  of  temperas." 

It  is  evident  that  in  his  time  it  was  well  known  that  paint 
required  age,  at  least  a  year,  to  reach  a  condition  of  permanence. 
He  devotes  several  chapters  to  the  subject  of  painting  with  linseed- 
oil;  he  also  describes  gold  size  (doratura),  which  was  made  of 
linseed-oil,  boiled  on  the  fire,  in  which  was  ground  some  white 
lead  and  verdigris;  to  this  was  added  some  varnish  resin,  and 
the  whole  was  boiled  all  together  for  a  short  time.  This  was 
applied,  as  thin  a  coat  as  possible,  and  left  until  the  next  day, 
when  it  was  tried  with  the  finger,  and  if  tacky  it  was  ready  for 
the  application  of  the  gold-leaf.  He  adds  that  this  is  made  for 
immediate  use;  if  it  is  to  be  kept  in  stock  the  verdigris  is  to  be 
omitted. 

The  whole  of  Cennini' s  treatise,  which  was  translated  into 


346  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

English  by  Mrs.  Merrifield  (who  also  translated  several  other 
Italian  treatises  on  art  of  much  interest)  in  1844,  is  worthy  of 
careful  study;  the  more  so  since  he  wrote  at  the  time  when  the 
art  of  painting  was  about  to  receive  its  greatest  advancement. 
It  is  said  that  the  method  of  painting  with  oil  as  vehicle  was 
discovered  by  Jan  Van  Eyck,  a  Flemish  painter,  otherwise  called 
John  of  Bruges,  in  1410.  Cennini's  treatise  was  written  several 
years  after  this  date,  but  he  was  at  the  time  of  its  writing  an  old 
man,  and  he  expressly  says  that  his  methods  are  those  of  the 
middle  of  the  preceding  century.  It  is  clear  that  oil  as  a  vehicle 
was  not  first  used  by  Van  Eyck;  it  was  known  to  Eraclius,  to 
Theophilus,  and  as  has  been  seen  in  an  earlier  chapter,  was 
used  in  England  in  the  thirteenth  century.  Cennini  says  it  was 
in  common  use  in  Germany ;  and  it  is  probable  that  it  was  known 
throughout  the  whole,  or  nearly  the  whole,  of  the  Christian  era. 
Van  Eyck  no  doubt  invented  something;  but  it  was  some  improve- 
ment in  materials  and  processes,  not  something  radically  new. 
All  the  experts  agree  that  his  paintings,  and  those  of  his  pupils, 
are  made  with  an  oleo- resinous  varnish  as  a  vehicle;  but  he  did 
not  invent  the  varnish,  nor  was  he  the  first  to  use  it  as  a  vehicle, 
for  Cennini  says  that  varnish  is  the  most  powerful  of  all  vehicles. 
It  is  possible  that  he  first  saw  the  advantage  to  be  gained  by 
thinning  varnish  with  turpentine;  none  of  the  recipes  prior  to 
his  time  speak  of  this,  and  it  seems  to  have  been  the  common 
practice  to  rub  the  varnish  on  with  the  finger,  which  would  be 
correct  if  it  were  not  thinned;  it  is  expressly  stated  that  it  will 
be  too  thick  if  laid  on  with  a  brush.  To  adapt  it  to  artistic  paint- 
ing it  must  have  been  thinned;  the  paintings  made  with  it  by 
the  great  masters  show  brushwork  of  the  most  skilful  and  deli- 
cate sort. 

In  illustration  of  this  it  will  be  interesting  to  quote  one  or 
two  authorities.  Gulick  and  Timbs,  whose  book  was  published 
in  1859,  say: 

"Probably  every  person  who  sees  for  the  first  time  a  picture 
by  Van  Eyck,  if  not  surprised  by  its  antiquated  treatment  or 
quaintness  of  expression,  will  be  very  much  astonished  to  find  that 


CONCLUSION.  347 

the  work  of  the  reputed  inventor  of  oil-painting  has  preserved 
its  brilliancy  of  tone  after  the  lapse  of  more  than  four  centuries 
far  better  than  most  pictures  executed  within  the  last  hundred 
or  even  the  last  fifty  years.  By  'brilliancy  of  tone'  we  do  not 
mean  the  force  and  depth,  the  luscious  richness  of  color  and  ful- 
ness of  effect  which  are  the  principal  charms  of  painting  in  oil, 
as  exhibited  particularly  by  the  Venetian  school;  but  that  the 
color  of  Van  Eyck,  though  quiet,  will  still  be  vigorous  and  fresh; 
that  it  will  have  limpid  transparency,  and  an  almost  illusive 
vacuity  of  space.  In  addition  to  this,  it  will  exhibit  an  amount 
of  truthful  realization  of  the  most  minute  and  exquisitely  delicate 
details  which  is  scarcely  ever  found  united  with  the  same  imperish- 
able durability  elsewhere. 

"These  characteristics  distinguish  more  or  less  all  the  early 
Flemish  pictures;  and  from  persons  habitually  engaged  in  restor- 
ing them  we  learn  that  the  colors  of  these  pictures  are  mostly  of 
a  harder  body  than  those  of  a  later  date;  they  resist  solvents 
much  better;  and  if  rubbed  with  a  file,  they  show  a  shining 
appearance,  resembling  a  picture  painted  in  varnish.  Examina- 
tion of  the  pictures  themselves,  and  the  researches  of  several 
learned  writers  within  the  last  few  years,  leave  us  no  room  to  doubt 
that  their  durability  is  attributable  chiefly  to  the  vehicle  employed, 
and  that  the  colors  were  used  not  simply  with  oils,  but  with  an 
oil- varnish  of  the  kind  we  call  'hard,'  or  in  other  words,  an 
oleo-resinous  vehicle,  such  as  might  strictly  be  employed  as  a 
varnish  over  a  picture  when  finished." 

The  same  authors  say  in  another  place  that  "it  is  probable 
that  varnishes  composed  of  resins  dissolved  in  oil  have  been  used 
in  the  most  ancient  times.  Beyond  all  doubt  the  composition  of 
varnish  was  known  in  Persia,  India,  and  China  before  the  best 
period  of  painting  in  Greece;  and  it  is,  then,  not  to  be  supposed 
that  the  Greeks  were  unacquainted  with  this  art." 

Another  well-known  English  critic,  Sarsfield  Taylor,  who 
wrote  in  the  first  half  of  the  last  century,  says : 

"That  he  [Van  Eyck]  had,  whether  he  did  or  did  not  invent 
it,  a  very  superior  vehicle  for  painting  is  unquestionable;  and 


348  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

his  pictures,  after  having  been  above  four  centuries  painted,  are 
almost  in  as  bright  and  firm  a  state  as  when  they  first  came  off 
the  easel.  It  is  feared  that  his  secret  has  long  been  lost,  and 
that  it  was  not  the  ordinary  mixture  of  oils  and  colors,  such  prob- 
ably as  was  used  here  [in  England]  at  that  time,  is  very  evident; 
for  none  of  our  early  oil-color  pictures  can  stand  any  competition 
with'  those  of  John  and  Herbert  Van  Eyck  for  clearness  of  light 
and  shade,  brightness  of  hues,  or  state  of  preservation;  it  has  all 
the  same  advantages  over  works  of  the  French  school  painted 
two  or  three  centuries  ago." 

It  may  well  be  noted  in  connection  with  the  numerous  formulas 
for  making  varnish  known  in  times  earlier  than  that  of  Van 
Eyck,  that  Facius,  an  Italian  historian  contemporary  with  that 
painter,  says  that  Van  Eyck  was  familiar  with  the  writings  of 
the  ancients. 

Eastlake  relates  that  the  English  landscape  painter,  Fair- 
field,  had  learned  the  use  of  oleo- resinous  varnish  as  a  vehicle 
from  the  Dutch  painter  Van  Strij,  who  was  a  successful  imitator 
of  Cuyp,  and  though  not  a  contemporary  of  that  painter  was 
well  acquainted  with  his  methods;  and  he  assured  F airfield  that 
hard  copal  or  amber  varnish  was  Cuyp's  ordinary  medium.  This 
agrees  with  the  remarkable  hardness  of  Cuyp's  paintings;  and 
this  seems  to  be  a  consecutive  tracing  back  of  this  vehicle  for  a 
period  which  now  amounts,  if  we  reckon  to  the  elder  Cuyp, 
whose  processes  appear  to  be  the  same  as  those  of  his  more  famous 
son,  to  nearly  or  quite  three  hundred  years.  Rembrandt  is  said 
by  his  contemporaries  to  have  painted  with  amber  varnish;  and 
Sir  Joshua  Reynolds,  who  was  always  experimenting  with  vehicles 
and  pigments, — it  is  said  that  he  destroyed  pictures  by  the  older 
masters  to  get  the  materials  for  analysis, — and  was  certainly 
competent  to  form  a  correct  opinion,  said  that  Rubens  used  oleo- 
resinous  varnish  as  a  vehicle.  Leonardo  da  Vinci,  certainly  one 
of  the  greatest  of  Italian  painters,  is  commonly  said  by  con- 
noisseurs to  have  used  varnish  as  a  vehicle;  and  about  1515  he 
was  commissioned  to  paint  a  picture  for  Pope  Leo  X.  Vasari 
relates  the  story  in  his  Lives  of  the  Painters.  It  seems  that 


CONCLUSION.  349 

Da  Vinci  had  recently  come  to  Rome.  As  was  common  practice 
among  artists  he  prepared  his  own  materials,  and  not  having  yet 
had  time  to  supply  himself,  he  began  first  to  make  them.  Leo 
inquired  the  cause  of  the  delay  and  was  told  that  the  painter 
was  getting  oils  and  resins  to  make  his  own  peculiar  varnish. 
This  the  Pope  criticised,  thinking  that  varnish  was  the  last  thing 
needed,  as  was  indeed  the  case  with  distemper  painting.  The 
painter  became  angry  and  left  the  court. 

Various  authorities  might  be  quoted  to  show  that  the  use  of 
oleo- resinous  vehicles,  which  rendered  a  final  varnish  needless, 
was  common  still  in  Flanders  in  the  seventeenth  century. 

As  we  come  down  to  more  recent  times  it  becomes,  of  course, 
easier  to  find  more  material;  but  enough  has  been  said  to 
satisfy  the  reader  that  the  extreme  durability  of  the  work  of 
the  great  masters  of  painting  was  connected  with  their  use  of 
amber  varnish  or  its  equivalent.  If  the  reader  will  remember 
what  has  also  been  said  in  a  former  chapter  of  the  value  of  a 
white  background  and  the  use  of  semi- translucent  paints  over  it, 
and  will  then  note  the  readiness  with  which  such  paints  may  be 
made,  even  with  very  opaque  pigments,  by  mixing  them  with 
varnish,  and  the  difficulty  of  doing  this  with  the  vehicles  in  earlier 
use,  even  with  oil,  it  will  be  plain  that  this  vehicle  added  so  greatly 
to  the  brilliancy  of  pictures  that  a  new  era  was  opened;  men  of 
artistic  taste  were  irresistibly  attracted  to  this  new  art,  and  so 
arose  the  great  revival  and  renewal  of  the  painters'  art.  If  it  be 
said  that  the  same  reasons  exist  now  and  that  nevertheless  the 
use  of  varnish  has  again  given  place  to  oil,  the  answer  is,  first, 
that  the  early  painters  had  very  few  colors,  and  to  get  intermediate 
effects  painted  a  thin  color  over  one  already  laid  on,  while  modern 
painters  have  an  almost  indefinite  variety.  Sir  Humphrey  Davy, 
who  gave  great  attention  to  this  matter,  states  that  "the  earlier 
Grecian  masters  used  only  four  colors,  namely,  Attic  ochre  for 
yellow,  sinopis  for  red,  the  earth  of  Melos  for  white,  and  black." 
Ivory-black  is  said  to  have  been  invented  by  Apelles.  Boschini 
relates  a  remark  of  Titian,  that  whoever  would  be  a  painter  should 
be  well  acquainted  with  three  colors,  and  have  perfect  command 


350  TECHNOLOGY  OF  PAINT  AND   VARNISH. 

over  them,  namely,  white,  red,  and  black.  Cennini  recommends 
only  twelve  pigments,  ten  of  which  could  be  used  in  oil;  he  knew 
no  brown  pigment,  though  modern  painters  have  fifteen  or  twenty 
of  this  color.  The  second  answer  is,  that  in  fact,  so  far  as  we  can 
judge,  modern  paintings  do  not  equal  those  of  the  masters  of  the 
middle  ages  in  permanence.  As  has  been  before  remarked,  the 
unequalled  facility  with  which  oil  can  be  used  has  been  the  cause 
why  it  has  displaced  varnish.  For  glazing  colors  some  painters 
now  use  a  mixture  of  mastic  varnish  and  boiled  linseed-oil,  called 
megilp.  This  has  been  used  for  many  years;  but  it  was  known 
and  discarded  by  the  artists  who  lived  before  Van  Eyck.  In 
Vasari's  life  of  Antonello  da  Messina  he  informs  us  that  the 
painter,  when  seeking  for  a  vehicle,  had  tried  the  experiment  of 
mixing  liquid  varnish  with  their  oil  colors,  and  that  the  result  had 
been  unsatisfactory.  The  translator  of  Cennini  says:  "It  is  some- 
what curious  that  the  painters  of  the  nineteenth  century  should 
have  revived  and  practised,  as  a  new  invention,  what  those  of  the 
fourteenth  century  had  tried  and  rejected;  and  more  extraordinary 
still,  that,  unwarned  by  experience,  they  should  continue  to  use 
it,  in  spite  of  the  awful  gashes  and  cracks  that  disfigure  the  pic- 
tures painted  with  this  vehicle." 

The  literature  of  paint  and  varnish  as  now  technically  used 
really  begins  in  the  last  part  of  the  eighteenth  century;  the  first 
notable  treatise  is  that  by  Watin,  published  in  1772.  This  author 
was  familiar  with  the  art  of  varnish-making,  and  gives  explicit 
directions  for  making  oleo- resinous  varnishes,  spirit  varnishes, 
and  those  made  by  dissolving  resins  in  the  essential  oil  of  turpen- 
tine. The  book  passed  through  many  editions;  it  contains  direc- 
tions for  executing  a  great  variety  of  work  in  painting,  varnish- 
ing, and  gilding.  A  general  idea  of  Watin's  knowledge  of  var- 
nish-making may  be  had  by  reading  his  precepts,  or  general  prin- 
ciples, which  he  made  for  the  guidance  of  his  readers. 


CONCLUSION.  351 

ON  THE  COMPOSITION  OF  OLEO-RESINOUS  VARNISH. 

I. 

Copal  and  amber  are  the  two  principal  substances  used  in 
oleo- resinous  varnish;  each  of  these  two  materials  combines  solid- 
ity and  transparence,  which  are  the  primary  qualities  of  varnish. 

II. 

Copal  and  amber  are  not  used  together;  copal,  being  whiter, 
is  reserved  for  the  more  transparent  varnishes;  amber,  a  harder 
resin,  serves  for  gold  varnish  or  to  make  varnish  to  be  used  over 
dark  colors. 

III. 

Amber  and  copal  can  be  dissolved,  as  has  been  already  said, 
in  oil,  but  we  believe  it  is  a  better  plan  to  melt  them  alone  over  a 
naked  fire.  By  so  doing,  they  are  less  liable  to  be  scorched  and 
are  always  whiter  and  more  clear.  When  we  dissolve  them  in  oil 
they  darken,  for  as  they  are  difficult  to  dissolve  it  is  necessary  to 
have  a  very  violent  fire. 

IV. 

The  oil  which  is  employed  either  to  dissolve  or  to  mix  with 
the  melted  resin  ought  to  be  perfectly  clarified  and  as  pale  as 
possible.  It  is  not  permitted  to  use  any  oil  in  making  varnish 
which  is  not  siccative,  otherwise  it  would  never  dry. 

V. 

To  dissolve  amber  or  copal  it  is  necessary  to  cook  them  alone 
and  dry;  and  when  they  are  well  melted,  which  is  known  by  their 
fluidity,  we  are  to  add  the  proper  quantity  of  prepared  fixed  oil. 

VI. 

Never  put  several  ingredients  together  to  dissolve  or  melt, 
since  the  more  manageable  will  be  first  liquefied  and  will  be  scorched 
before  those  which  offer  more  resistance  will  have  arrived  at  the 
like  condition. 


3$2  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

VII. 

To  melt  the  resins  it  is  proper  to  have  a  glazed  earthen  pot 
which  can  be  covered  with  a  lid.  This  must  not  be  full  because 
we  are  to  add  to  it  the  oil  and  spirit  of  turpentine,  and  there  must 
be  room  besides  for  it  to  swell  up  without  overflowing. 

VIII. 

Set  the  glazed  earthen  pot  containing  the  resin  over  a  naked 
fire  of  glowing  charcoal  which  does  not  blaze,  for  fear  of  setting 
fire  to  the  contents. 

IX. 

In  fusing  the  resins  avoid  heating  them  too  much.  They  will 
turn  black  and  lose  their  valuable  qualities;  too  much  scorched 
they  will  be  of  no  use. 

X. 

We  recognize  that  the  resin  is  in  the  proper  state  of  fluidity  to 
receive  the  oil  when  it  offers  little  resistance  to  the  iron  stirring- 
rod  and  runs  off  from  it  drop  by  drop. 

XI. 

When  we  are  ready  to  incorporate  the  oil  with  the  melted  resin, 
it  ought  to  be  very  hot,  almost  boiling,  but  it  ought  to  be  well 
purified  and  clarified.  It  is  necessary  to  heat  it  only  at  the  moment 
when  it  is  to  be  used.  If  it  is  used  cold  it  will  dissolve  less  often 
melted  resin,  and  by  cooling  will  harden  it;  while  if  both  are  of 
the  same  temperature  they  will  be  rendered  more  compatible. 

XII. 

Do  not  add  the  prepared  oil  until  the  resin  is  completely 
fluid,  ready  to  receive  it,  which  will  occur  only  after  it  has  boiled 
up  several  times.  In  adding  the  oil,  turn  it  in  little  by  little, 
stirring  it  always  with  the  spatula.  Let  the  mixture  finally  be 
united  by  boiling  it  up  several  times  over  the  fire. 


CONCLUSION.  353 

XIII. 

When  the  oil  appears  cooked  with  the  resin,  take  away  the 
pot  from  the  fire,  and  when  it  has  partly  cooled  and  is  only  warm 
turn  in,  with  constant  stirring,  the  spirit  of  turpentine,  which  ought 
to  be  in  larger  quantity  than  the  oil.  If,  when  the  spirit  of  tur- 
pentine is  added,  the  oil  is  too  hot,  the  spirit  will  take  fire  and 
burn  the  varnish. 

XIV. 

Skilful  manipulators,  when  they  wish  to  make  a  very  fine 
varnish  of  copal  or  amber,  do  not  wait  until  all  the  resin  is  melted. 
When  the  greater  part  is  boiling  and  appears  to  rise  up  and 
then  settles  down,  then  they  add  the  oil,  which  combines  with  the 
part  of  the  resin  which  is  melted  and  does  not  dissolve  that  which 
is  not  yet  fused.  By  this  means  the  copal  and  amber  are  not 
subjected  to  a  too  prolonged  heat  and  are,  therefore,  more  clear 
and  more  beautiful.  If,  when  the  oil  is  incorporated,  the  oper- 
ator tries  to  dissolve  the  unmelted  resin,  then,  as  I  have  already 
said,  he  darkens  the  varnish. 

XV. 

The  varnish  being  made,  it  is  necessary  to  be  careful  to  strain 
through  a  cloth,  to  remove  any  foreign  matter  which  may  be  in  it. 
If  any  unmelted  pieces  are  found  these  must  not  be  put  back  on 
the  fire  with  the  melted  resins,  as  this  would  result  in  making 
the  varnish  dark  in  color. 

XVI. 

You  may  put  the  pieces  of  unmelted  gum  by  themselves  into 
the  earthen  pot  and  recommence  to  liquefy  them,  afterward 
adding  oil  and  spirit  of  turpentine;  but  you  may  be  sure  that  the 
second  varnish  will  not  be  as  white  as  the  first,  for  the  reason 
that  the  resin  has  been  impregnated  with  oil  and  will  turn  dark 
in  cooking.  If  one  does  not  wish  to  use  up  immediately  these 
pieces  of  copal  or  amber,  and  if  one  has  the  time  to  let  them  dry 
in  the  sun  and  separate  them  from  their  oil,  they  may  subse- 
quently be  used  as  though  they  had  never  been  treated. 


354  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

XVII. 

Let  the  varnish  settle  at  least  twice  twenty-four  hours  to 
clarify  it.  The  longer  it  stands  the  more  it  will  clear  and  it  does 
not  clear  so  quickly  as  spirit- of -wine  varnish. 

XVIII. 

Oleo-resinous  varnish,  if  properly  kept,  becomes  more  beauti- 
ful, but  grows  thicker.  It  is  necessary,  when  one  is  ready  to  use 
it,  to  mix  with  it  a  little  spirit  of  turpentine  and  to  heat  it  for  a 
time  in  a  water-bath.  This  clears  it. 

XIX. 

When  we  wish  to  make  fine  pale  oleo-resinous  varnish,  it  is 
necessary  each  time  to  use  a  new  melting-pot,  for  usually  the 
action  of  the  fire  cracks  the  glaze,  and  the  oil  and  turpentine 
enters  these  cracks  and  penetrates  the  earthenware.  Then  when 
we  again  attempt  to  melt  resins,  these  liquids  which  have  been 
absorbed  ooze  out  and  burn  and  mix  with  the  resins  and  blacken 
them.  Those  who  do  not  use  this  precaution  will  be  much 
surprised  to  not  have  the  same  result  as  before,  and  t  will  not 
know  to  what  to  attribute  this  accident. 

XX. 

In  fine  summer  weather  these  varnishes  ought  to  dry  in  twenty- 
four  hours.  In  the  winter  the  varnished  objects  are  usually  put 
in  ovens  or  in  a  room  where  there  is  a  hot  fire.  They  dry  more 
or  less  rapidly  according  to  temperature. 

XXI. 

The  oil,  as  has  been  observed,  is  incorporated  with  the  resins 
only  to  preserve  them  in  a  fluid  condition  and  prevent  them  from 
coagulating;  but  as  the  oil  is  thick,  the  spirit  of  turpentine  ren- 
ders it  more  freely  flowing,  more  easy  to  spread  and  to  dry. 

XXII. 

It  is  necessary  to  use  spirit  of  turpentine,  without  which  the 
varnish  will  never  dry.  The  quantity  is  commonly  double  that 


CONCLUSION.  355 

of  the  oil.  We  use  less  turpentine  in  summer  because  the  oil, 
drying  more  quickly  by  the  heat  of  the  sun,  becomes  thick  more 
rapidly  and  the  work  dries  from  the  bottom.  On  the  other 
hand,  in  the  winter,  when  the  heat  is  less,  and  often  only  arti- 
ficial heat,  we  put  in  less  oil  so  that  the  varnish  may  dry  more 
quickly,  but  we  also  add  more  spirit  of  turpentine,  which  evapo- 
rates more  easily. 

XXIII. 

The  less  oil  there  is  the  harder  and  quicker  drying  is  the 
varnish;  as  the  oil  is  increased  it  loses  its  body,  but  it  spreads 
more  easily. 

XXIV. 

A  very  large  proportion  of  oil  in  a  varnish  hinders  its  drying^ 
and  if  there  is  too  little,  it  cracks.  It  is  not  possible  to  deter- 
mine the  precise  quantity.  The  ordinary  proportion  is,  to  incor- 
porate with  each  pound  of  copal  or  amber  from  a  quarter  to  a  half 
pound  of  oil. 

GENERAL  PRECEPTS  ON  THE  MAKING  OF  VARNISH. 

I. 

All  varnish  ought  to  contain  material  which  is  durable  and 
brilliant.  These  two  qualities  constitute  the  beautiful  and  the 
good  in  varnish.  It  ought  to  be  very  quick- dry  ing,  hence  it  is 
necessary  that  the  liquids  which  are  employed  to  dissolve  the 
materials  should  be  perfectly  dehydrated  and  siccative 

II. 

All  bitumens  and  resins  suitable  for  making  varnish,  if  they 
are  heated  too  much,  will  become  burnt  when  they  are  brittle 
and  may  be  reduced  to  powder,  and  when  we  try  to  polish  them, 
we  find  they  are  worthless. 

III. 

It  is  necessary  to  clean,  select,  and  break  into  little  pieces  all 
the  resins  used  in  making  varnish  but  not  to  reduce  them  to 


356  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

powder  before  melting,  because  the  powdered  resin  will  stick 
to  the  sides  of  the  interior  of  the  vessel  and  very  easily  become 
scorched.  It  is  most  easily  melted  when  it  is  in  little  pieces. 

IV. 

It  is  forbidden  by  various  regulations  to  make  varnish  in  the 
middle  of  towns.  This  is  a  prudent  policy.  The  Tesins  are  so 
combustible,  they  are  able  to  cause  serious  fires;  besides  which, 
their  odor  is  so  penetrating  that  it  is  noticeable  at  a  distance  and 
is  disagreeable  to  the  neighborhood;  so  that  varnish-makers  are 
obliged  to  work  outside  the  city  limits  and  in  the  country.  They 
are  not  so  particular  in  regard  to  spirit- of- wine  varnishes,  yet  they 
are  not  less  dangerous.  It  is  important  that  one's  attention  should 
be  constantly  on  the  work,  and  to  take  every  precaution  against 
accident.  It  is  necessary  to  make  all  solutions  by  day  and  to 
avoid  artificial  light.  If  the  operator,  working  in  an  obscure 
place,  should  wish  to  bring  a  wax  taper 'or  a  lighted  candle  near 
the  work,  the  vapor  of  the  resins,  the  spirit  of  wine,  or  the  oil 
may  take  fire  and  cause  a  conflagration.  It  is  necessary,  in  case 
of  accident,  to  have  several  sheepskins  or  calfskins,  or  cloths 
folded  in  several  thicknesses,  always  kept  wet,  to  throw  over  the 
vessels  which  contain  the  varnish  materials,  to  smother  the  flame. 

V. 

The  action  of  fire  serves  to  combine  the  liquids  and  resins 
which,  by  their  union,  make  varnish,  but  it  is  not  possible  to 
determine  the  time  during  which  the  heat  must  be  applied;  that 
depends  on  the  tensity  of  the  fire,  which  should  be  kept  perfectly 
steady,  neither  increasing  nor  diminishing. 

VI. 

If  the  workmen  should  get  burned,  in  order  to  prevent  blisters, 
the  wound  should  be  at  once  wet  with  spirit  of  wine,  or  wrapped 
with  a  compress  wet  with  spirit  of  wine,  then  cover  the  wound 
with  a  plaster  of  olive-oil  and  litharge  which  have  been  rubbed 
together  until  they  become  a  smooth  pulp. 


CONCLUSION.  357 

VII. 

Varnish  is  sometimes  made  of  various  colors.  The  Dictionnaire 
Economique  gives  numerous  recipes,  but  such  varnishes  are  less 
fine  than  the  others.  The  substances  which  are  put  in  to  color 
them  change  their  character  and,  not  dissolving,  always  form  a 
sediment  which  dulls  the  surface.  It  must,  therefore,  be  remem- 
bered that  it  is  much  better  to  apply  a  suitable  color  first  and 
afterward  put  on  the  varnish,  which,  if  it  has  been  well  made, 
will  not  at  all  change  the  tone  of  the  colors. 

VIII. 

A  general  rule,  which  should  never  be  forgotten,  is  to  ahvays 
keep  perfectly  clean  and  well  stoppered  the  vessels  which  hold 
the  materials  from  which  the  varnish  is  to  be  made  as  well  as 
those  in  which  it  is  to  be  kept,  for  nothing  evaporates  so  easily  as 
a  varnish;  and  a  varnish  which  evaporates  becomes  thick  and 
darkens  and  changes  the  colors  over  which  it  is  used. 

IX. 

When  the  varnish  is  made,  it  is  carefully  purified,  as  much 
as  is  possible,  from  all  dirt  and  dust,  by  passing  it  through  a 
strainer  of  silk  or  fine  linen,  and  when  it  is  purified,  care  should 
be  taken  to  close  the  bottle  which  contains  it,  for  fear  that  par- 
ticles of  dust  may  fall  into  it. 

X. 

The  nature  of  the  object  to  be  varnished  should  determine  the 
kind  of  varnish  to  be  used.  If  it  is  to  be  exposed  to  the  weather, 
it  is  necessary  to  use  an  oleo-resinous  varnish.  If,  on  the  con- 
trary, it  is  to  be  kept  within  doors,  cared  for,  and  preserved  in 
the  interior  of  the  house,  then  we  may  use  spirit-of-wine  varnish, 
which,  while  it  is  brilliant,  gives  off  no  odor,  dries  quickly,  and  is 
durable  as  long  as  it  is  not  too  much  exposed  to  the  air  and  the 
sun.  As  for  varnish  of  spirit  of  turpentine,  it  is,  except  such  as 
are  used  on  paintings,  hardly  deserving  the  name  of  varnish. 
Those  which  are  called  so  are  in  reality  commonly  composed  of 


358 


TECHNOLOGY   OF  PAINT  AND    VARNISH. 


common  resins  which  will  dissolve  together  and  of  which  the 
turpentine  is  the  foundation. 

XI. 

Oleo- resinous  varnishes  endure  easily  the  heat  of  the  sun, 
because  the  amber  or  the  copal  which  they  contain  are  too  durable 
to  be  changed.  Sandarac,  on  the  contrary,  which  is  the  base 
of  spirit-of-wine  varnish,  is  affected  by  the  sun  and  cannot  long 
resist  it  when  made  into  a  varnish.  This  one  often  sees  in  the 
heat  of  summer,  when  the  spirit-of-wine  varnish  on  the  interior 
of  rooms  suffers  decomposition  and  gives  off  an  odor,  as  if  it 
were  not  well  made. 

XII. 

Varnish  is  made  in  glazed  earthen  pots  which  are  commonly 
changed  at  each  operation,  for  a  reason  given  elsewhere. 


This  illustration  represents  a  varnish-maker's  furnace,  date  about  1778;  from 
the  thirteenth  volume  of  the  Oeconomische  Encyclopedic.  The  fuel  was  charcoal. 
The  resin  was  melted  and  the  varnish  made  in  the  flask. 

The  next  book  of  importance  was  the  "Painters'  and  Var- 
nishers'  Guide,"  published  in  Geneva  in  1803,  and  written  by 


CONCLUSION.  359 

P.  F.  Tingry,  a  chemist  and  scientific  man  of  some  note.  He 
was  a  member  of  the  Society  at  Geneva  for  the  Encouragement 
of  the  Arts,  Agriculture,  and  Commerce.  As  this  society  desired 
that  a  methodical  description  of  the  art  of  varnishing  should  be 
a  part  of  their  publications,  and  as  Tingry  had  lectured  both 
publicly  and  privately  on  the  subject,  they  requested  him  to 
undertake  the  work.  His  book  brought  it  up  to  about  a  third  of 
a  century  later  than  the  treatise  of  Watin.  It  passed  through 
numerous  French  and  at  least  two  English  editions.  He  notices 
the  fact  that  formulas  for  making  both  varnishes  and  colors  had 
long  been  known,  and  asserts  that  Watin  was  the  first  to  system- 
atically weed  out  the  useless  and  explain  the  sequence  of  the 
valuable  ones,  thus  establishing  a  method  of  study  which  sub- 
sequent writers  might  enlarge  and  perfect.  He  gives  twenty-nine 
varnish  formulae.  These  are  divided  into  five  classes,  or  genera, 
of  which  the  first  includes  three  kinds,  called  drying- varnishes 
made  with  alcohol.  Two  contain  only  mastic,  sandarac,  and 
Venice  turpentine  for  solid  ingredients;  the  third  contains  a 
small  amount  of  "powdered  copal  of  an  amber  color,"  and  pre- 
viously melted.  In  all  cases  these  are  made  in  batches  of  about 
one  -quart,  in  glass  flasks  immersed  in  hot  water,  stirred  contin- 
ually with  a  stick,  and  cleared  by  settling  with  powdered  glass. 
He  mentions  the  use  of  camphor  as  an  assistant  to  solution.  The 
second  genus  includes  seven  varnishes,  also  having  spirit  of  wine 
as  the  solvent,  made  in  the  same  quality  and  manner  as  those 
already  described,  but  less  drying  than  the  first  genus,  by  which 
he  means  less  hard  and  more  flexible.  The  various  ingredients 
are  sandarac,  elemi,  anima,  rosin,  shellac,  Venice  turpentine, 
mastic,  benzoin,  copal,  or  amber  (not  all  these  resins  in  any  one 
varnish,  but  three,  four,  or  five),  camphor  to  assist  the  solution, 
and  in  some  of  them  coloring-matter  was  added,  the  list  being 
dragon's-blood,  sandalwood  extract,  saffron,  gamboge,  and  ex- 
tract of  canna  indica.  In  all  cases  he  uses  10  or  12  ounces  of 
resinous  matters  to  a  quart  of  alcohol,  or  about  half  as  heavy  a 
varnish  as  our  modern  standard  shellac. 

This  third  genus  of  varnishes  has  spirit  of  turpentine  for  a 


360  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

solvent.  The  resins  are  mastic,  which  is  always  used  in  this  class, 
so  is  Venice  turpentine;  sandarac  and  seed- lac  are  also  used,  and 
coloring-matter  as  before.  These  varnishes  are  for  application 
to  finished  paints,  or  for  metals  and  wooden  boxes.  The  batch 
is  about  one  quart,  and  is  made  in  the  way  already  described. 
There  are  six  of  these  formulae. 

The  fourth  genus,  six  in  number,  is  based  on  copal,  by  which 
Tingry  meant  apparently  a  soft  copal  like  Manila.  At  all  events, 
it  was  wholly  soluble  in  ethylic  ether  ("sulphuric"  ether),  and 
partly  soluble  in  alcohol.  One  of  the  solvents  in  this  class  is 
essential  oil  of  lavender.  The  powerful  solvent  qualities  of  this 
liquid  are  believed  to  be  due,  at  least  in  part,  to  a  camphor  which 
it  contains.  He  also-  added  about  2  per  cent,  of  camphor  to  the 
oil  of  lavender.  The  principal  solvent  or  diluent  was  spirit  of 
turpentine.  It  is  worth  noting  that  one  of  these  varnishes  was 
suitable  for  the  varnished  wire  gauze  used  in  ships  instead  of 
glass. 

The  fifth  genus  comprises  what  he  calls  fat  varnishes,  or  oleo- 
resinous  varnishes.  The  materials  which  enter  into  their  com- 
position are  copal,  amber,  prepared  linseed-oil,  nut-  and  poppy- 
oil,  and  essential  oils,  especially  spirit  of  turpentine.  In  all  cases 
the  resin  was  first  melted  and  the  oil  afterward  added  to  it  in 
the  usual  manner.  Four  to  eight  ounces  of  resin  made  a  batch. 
Seven  formulae  are  given,  only  five  of  which  are  of  true  oleo- 
resinous  varnishes:  one  is  a  gold  size,  and  one  is  caoutchouc 
dissolved  in  oil.  His  own  preference  was  for  varnishes  of  the 
fourth  genus;  but  he  admitted  that  for  durability  oleo- resinous 
ones  must  be  used. 

He  gives  a  long  and  interesting  discussion  of  the  effect  of  light 
on  spirit  of  turpentine,  showing  that  it  increases  its  specific  grav- 
ity and  its  solvent  powers,  qualities  now  thought  to  be  due  to  the 
action  of  oxygen,  the  possibility  of  which  he  suggests. 

TINGRY' s  FURNACE  FOR  MELTING  RESIN. 

It  is  built  of  fire-clay.  The  cover  of  the  inner  tube,  C,  is  of 
iron,  which  may  be  luted  to  the  clay  or  porcelain  tube.  The  net 


CONCLUSION. 


361 


D  is  of  brass  wire,  woven  to  a  brass  ring  which  rests  in  the  coni- 
cal upper  extremity  of  the  tube.  The  upper  part  of  the  furnace 
is  filled  with  charcoal;  the  copal,  in  pieces  not  larger  than  a  nut, 
on  the  wire  net.  The  lower  end  of  the  tube  C  is  immersed  about 
i  in.  in  water  contained  in  a  suitable  capsule  F\  or  this  capsule 


mBHIHIIIIII!     ~~H 


may  contain  oil,  kept  hot  by  setting  the  capsule  on  a  plate  of  hot 
iron,  in  which  case  the  melted  resin  will  be  at  once  dissolved  by 
the  oil,  which  will  also  collect  the  products  of  distillation,  or  such 
parts  as  can  be  liquefied.  The  laboratory  furnace,  A  B,  is 
17^  insc  in  total  height,  the  interior  diameter  at  the  top  9^  ins., 
and  at  the  bottom  7  ins.  G  is  a  larger  furnace,  built  on  an  iron 
tripod.  But  the  inventor  says:  "I  must  always  insist  on  the  ad- 
vantage of  employing  not  more  than  6  ounces  of  resin  in  one 
operation." 

The  next  author  is  M.  Tripier-Deveaux,  who  published  in 
1845  a  "Theoretical  and  Practical  Treatise  on  the  Art  of  Varnish- 
making."  His  book  has  the  great  merit  of  having  been  written 
by  a  man  engaged  commercially  in  the  manufacture  and  sale  of 
varnish,  and  he  therefore  knew  what  varnishes  were  in  demand 
and  in  successful  use.  He  devoted  his  time  chiefly  to  varnishes 
composed  of  resins  dissolved  in  alcohol  and  in  turpentine,  and 
contributed  considerably  to  the  accuracy  of  our  knowledge  of 
these;  but  he  also  made  oleo- resinous  varnishes,  in  which  branch 
he  shows  most  advancement  in  preparing  oil  with  driers. 

In  1866  M.  Henri  Violette  published  a  treatise,  entitled  a 
" Practical  Guide  for  the  Manufacture  of  Varnish,"  valuable 


362  TECHNOLOGY   OF  PAINT  AND    VARNISH. 

from  a  historical  point  of  view,  but  apparently  not  the  work  of 
a  practical  manufacturer.  He  gave  much  more  careful  descrip- 
tion of  the  various  resins,  etc.,  than  any  of  his  predecessors,  and 
collected  what  chemical  and  other  scientific  information  was  at 
that  time  accessible  to  him.  His  detailed  accounts  of  the  prepa- 
ration of  drying  oils  with  litharge  and  oxide  of  manganese  are 
of  interest;  but  evidently  at  that  time  the  making  of  oleo-resinous 
varnishes  was  not  in  a  very  advanced  state  in  France.  We  know 
from  other  sources  that  these  varnishes  were  more  extensively 
made  in  England  at  that  time,  and  probably  also  in  the  United 
States;  but  we  have  no  books  of  importance  on  the  subject  in 
English,  as  the  English  and  American  makers  tried  to  keep  their 
processes  secret. 

In  Germany  the  most  notable  early  treatise  was  that  of  Dreme, 
a  book  similar  to  those  of  Watin  and  Tingry.  It  was  published 
in  1821  at  Brunn.  An  interesting  book  on  encaustic  painting 
by  Fernbach  ("  Die  enkustische  Malerei ")  was  published  at 
Munich  in  1845. 

Mention  should  also  be  made  of  a  paper  which  received  a 
gold  medal  from  the  Society  of  Arts,  London,  published  in  Vol.  49 
of  their  Transactions,  by  Mr.  J.  Wilson  Neil,  which  gives  a  de- 
tailed account  of  the  actual  operation  of  melting  the  resin  and 
combining  it  with  oil  and  turpentine.  It  is  interesting  from  a. 
historical  point  of  view,  but  contains  nothing  essentially  novel, 
and  very  little  that  is  practised  now.  It  is  to  be  found,  practically 
in  full,  in  Ure's  "Dictionary  of  the  Arts  and  Sciences,"  which  is  to 
be  found  in  almost  every  collection  of  technical  books. 

Within  the  last  half-century  several  books  on  varnish  have 
appeared,  and  some,  of  notable  merit,  on  pigments.  Some  of 
these  have  been  mentioned  in  preceding  chapters  of  this  book. 

One  of  the  most  serious  difficulties  of  the  subject  is  that  in 
different  countries  different  names  are  given  to  the  same  resin, 
and  the  same  name  to  different  resins.  Violette,  for  instance, 
describes  under  the  name  of  East  Indian  Copal  the  resin  now 
known  in  England  and  America  as  Zanzibar,  and  he  describes 
under  the  name  Zanzibar  a  soft,  "semi-hard"  resin  of  unknown 


CONCLUSION.  363 

origin.  Animi  is  a  name  the  value  of  which  can  never  be  known 
except  from  the  context;  and  even  when  we  speak  of  a  well- 
known  resin  like  Kauri  it  is  difficult  to  properly  describe  the 
grade.  What  is  known  in  the  New  York  market  as  No.  i  Kauri 
is  decidedly  inferior  to  the  resin  sold  under  the  same  name,  for 
about  one-third  the  present  price,  twenty  years  ago.  Some  of 
the  fine  African  resins  formerly  used  are  now  rare,  and  on  the 
other  hand  new  resins  are  appearing  on  the  market  every  year. 
For  these  and  other  similar  reasons  it  is  useless  to  give  formulae 
for  making  particular  varnishes.  Every  maker  is  gradually  chang- 
ing his  formulas  continually,  and  must  if  he  keeps  up  with  the 
improvements  of  the  art. 

The  writer  has  had  some  thoughts  of  giving  an  outline  of  tne 
chemical  work  which  has  been  done  on  varnishes,  but  it  would 
be  of  little  use.  Chemists  who  are  interested  have  usually  access 
to  the  original  papers,  published  in  the  various  chemical  journals. 
Methods  of  analysis  of  varnishes  and  paints  are  rapidly  changing, 
and  are  still  very  unsatisfactory.  Up  to  the  present  time  the 
ingenuity  of  the  manufacturer  has  been  able  to  keep  ahead  of  the 
skill  of  the  analyst.  It  is  to  be  hoped — and  I  am  glad  to  believe 
that  there  are  grounds  for  hope — that  our  analytical  methods 
will  be  greatly  improved  within  a  few  years.  At  present  every 
manufacturer  depends  finally  on  time  and  exposure  tests;  but 
let  a  warning  be  given  that  paints  and  varnishes  may  only  be 
tested  under  fair  conditions,  and  that  the  best  materials  will 
sometimes  give  bad  tests.  If  we  are  testing  several  varnishes  of 
the  same  class,  and  keep  repeating  the  tests  often  enough,  we 
will  finally  get  a  trial  in  which  the  best  varnish  shows  the  poorest 
result.  The  explanation  of  this  is  that  we  do  not  know,  or  can- 
not control,  all  the  conditions  of  the  test.  All  this  is  equally 
true  of  paints  and  varnishes. 

In  writing  on  this  subject  it  is  hard  to  tell  what  to  put  in 
and  what  to  leave  out.  If  the  writer  expresses  too  copiously 
his  own  experience,  the  technical  details  will  interest  only  those 
who  are  themselves  engaged  in  like  work,  and  who  may  be  pre- 
sumed to  have  as  much  knowledge  of  the  subject  as  himself; 


364  TECHNOLOGY  OF  PAINT  AND    VARNISH. 

and  these  observations  will  in  a  few  years  be  out  of  date  in  any  case. 
The  general  principles  involved,  and  the  established  and  approved 
methods,  are  the  essential  things.  These  may  be  comprehended 
by  those  who  will  give  the  subject  the  attention  it  deserves. 
Painting  is  an  Art  Whether  our  interest  in  it  is  as  a  fine  art  or 
an  industrial  art,  the  technical  principles  are  the  same;  and  it 
is  as  old  as  civilization  itself.  Its  practitioners  can  show  an  un- 
broken descent  from  "the  early  dusk  and  dawn  of  time."  They 
may  feel,  like  all  who  dignify  an  art  by  faithful  and  intelligent 
service,  that 

"The  gods  hear  men's  hands  before  their  lips, 

And  heed  beyond  all  crying  and  sacrifice 
Sight  of  things  done  and  noise  of  laboring  men." 


INDEX. 


PAGE 

Aetius 35 

Albert! ig 

Alcherius 14 

Alessio 36 

Allegheny  pipe  line 277 

Apelles   23,  334 

Aristotle 122 

Asphaltic  cement 184 

Asphaltum : 109,  266 

coating  on  pipe 266 

Architectural  metal  work 194 

Bacon,  Lord 24 

Banana  liquid . 117 

Barium  carbonate 121,  311 

"         sulphate 121,  311 

Berenice 27 

Boiled  oil 40,  89 

Boneblack   131 

Boston  Stone 138 

Brick-dust 18,  155 

Bridge-painting 195 

Brilliance  of  varnish 329 

Bromine,  action  of 46 

Brushes 338 

Brush-safe 338 

Burning-off  paint 325 

Burgundy  pitch 107 

Bunghole  oil 41 

Callimachus 27 

Calomino , 30 

Cambridge  pipe  line 277 

Caneparius 19 

Carriage-painting 301 

365 


3  66  INDEX. 

PAG2 

Catullus 27 

Cellars,  painting 323 

Cennini 14,  31,  123,  341,  343,  350 

Chairs,  varnishing 328 

China  wood-oil 85 

Chinese  blue 126 

Chinese  lacquer 146 

Chrome  green 125 

"  oxide....' 126 

*'  yellow 124 

Cicero 23,  24,  334 

Coal-tar  coatings,  modern 261 

Coating  steel  at  the  mill . .  204 

Cobalt 37 

"  blue T 126 

Collodion 113 

Colophony 16,  95 

Copal 29 

Copper  on  ships'  bottoms 290 

Copper  oxide  paint 292 

Copper  soap  paint 294 

Corrosion  of  iron,  conditions  which  promote 181 

Corrugations  of  pipe  coating 270 

Cost  of  paint 251 

Cost  of  painting 248 

Covering  capacity  of  paint  (area)  , 249,  314 

Covering  power  of  paint  (opacity) 142 

Crevices,  how  treated 206 

Cuyp 348 

Damar..., 105,  140,  300 

Damar  enamel  paint 140 

Dark  varnishes 329 

Davy,  Sir  Humphry 349 

Dead-oil  of  coal-tar 264 

De  Mayerne  MS 37,  337 

Diminished  flow  of  water  in  rusty  pipe 259 

D'Incarville's  memoir 146 

Dioscorides 23,  36,  340 

Distemper 4,  311 

Dreme 362 

Driers 33,  40,  88,  312 

"       bad  effects  of 92 

' '       from  soap 90 

"       low-temperature 92,  312 

"       self-drying 93 


INDEX.  367 

PAGE 

Eastlake 25,  122,  337,  348 

Economy  in  painting 248 

Egyptian  varnish r 7,  8,  21 

Elastic-undercoat  cracks 303 

Electron 29 

Elemi 107 

Enamel  coatings  in  U.  S.  Navy 278 

"         on  bridge-work 279 

paint .   140,  248 

' '     for  steel  structures 248 

Encaustic  painting 4,  25 

Enzymes 178 

Eraclius 37,  342 

Eustathius 28 

Facius   348 

Fair  field. ... 348 

Ferment  of  Japanese  lacquer 175,  178 

Fernbach 362 

Fillers. .......    315 

Finishing  varnish 309 

Fireproof  paints 322 

Fish-oil 134 

Floor  finishing 318 

Floor-wax 4,  319 

Fortunato 30 

Frankincense n,  25,  29 

Furniture-varnishing 327 

Galen 23,  36 

Gentileschi .  .      337 

Glassa 13,  14,  29 

Glue 8 

Grease  paints 6 

Greek  pitch '. . . . .    16,  17 

Grinding  Japan 135 

Guide-coat 307,  343 

Gulick  and  Timbs 346 

Hippocrates 23 

House-painting 311 

Incense n 

Influence  of  weather  on  painting 254 

Iron  in  nature 180 

Iron  oxides 128 

"         "       permanence  of 129,130 


INDEX. 

PAGE 

Ivory-black 131 

Jacobus  de  Tholeto 15 

Japan 87,  91,  312 

"      grinding 93,  135 

John.J.  F 7 

Juniper  resin n,  15,  19 

Karabe 29 

Kodak  films 113 

Knifing-lead 304 

Knots 313 

Laboratory  tests  of  paint  incomplete 244 

Lacquer,  Chinese 146 

"        colored 115 

Lampblack 132 

Laniere 337 

Lead  paints 212 

Lead  compounds  in  varnish 38,  87 

Lead  sulphate 120 

"     white 119 

Leather,  artificial 116 

Leonardo  da  Vinci 32,  122,  348 

Leonidas 24 

Libravius 19 

Linseed-oil,  bleached 35 

"  breaking  of 34 

"  mucliage  in 34 

"  oxidation  of 3,  35 

"        %  phosphates  in 34 

"  saponification  of 51 

"  specific  gravity  of 43 

"  tests  for 43,62 

Linoxyn 3,  35,  133 

Litharge. . .    19 

Lithopone 120 

Livache's  test 60 

Lucca  MS 28 

Mcllhiney , 38,  39 

Mcllhiney's  bromine  process 47 

Maltha no 

Manganese * 37 

Mappae  Claviculi 28 

Marcellus 36 


INDEX.  369 

PAGE 

Marcian  MS 16 

Mastic 16,  107 

Mathioli , 19 

Maumene  test 59 

Merrifield,  Mrs 337,  346 

Mercurial  paints 294 

Metal  roofs 320 

Mills  for  paint 135,  138 

Mill-scale 190 

Mineral  oil,  detection  of 53 

Minium 15 

Minutoli •..       7 

Mixer 133 

Molecular  structure  affects  corrosion 220 

Neil,  J.  W ' 362 

Nero 28 

Nicias 23,  334 

Nickel 37 

Oil  of  cedar 22 

Oil  paint 118 

"       "     for  structural  metal 210 

Old  furniture,  refinishing 334 

Olibanum 25 

Ovid 28 

Oxides  of  iron « 128 

"        "    "     permanence  of 129,130 

"  P.  &  B."  paint no 

Paint 4 

"     in  I3th  century 10 

"     as  engineering  material, 186 

"     films,  thickness  of 185 

"     removers 326 

"     tests 217 

Paris  green 125 

Paste  color 133 

Perilla  oil 168,  176 

Petitot 37 

Pickling  metal 202 

Pigments 4,  119,  133 

"          fineness  of   118,123 

Plaster,  to  paint .' 323 

Pliny 23,  28,  334,  340 

Poisonous  quality  of  Chinese  varnish 148 


37°  INDEX. 

PAGE 

Polishing  varnish 157,  171,  330 

Portland  cement  to  protect  iron , 181 

Pounce 5 

Praxiteles 23 

Price  of  Japanese  lacquer 177 

Priming  coat 313 

Protective  distinct  from  decorative  coatings 187 

Protogenes 23 

Prussian  blue 126 

Putty   305,  314,  324 

Pyroxylin 112,  114 

Quin's  memoir  on  lacquer 165 

R.  Angus  Smith  patent 259 

Red  lead 213 

Refraction,  index  of 61 

Rein's  treatise  on  lacquer 174 

Reinforced  concrete 182 

Rembrandt 348 

Reports  on  painting  unreliable 216 

Resins. 72,  78 

"      tinctorial 108 

Reynolds,  Sir  Joshua 348 

Rochester  pipe  line 274 

Roofs 320 

Rossello 18 

Rosin 95 

"      and  lime , 96 

"       varnish 97 

"  "          cracks  in   « 98 

"  "          rubbing  test  for 102 

sponge  test 101 

Rough-stuff 306,  342,  343 

Rubbing-varnish 156,  170,  308 

Rub-lead 304 

Rusting  of  cast  iron 258 

"         "    water-pipe 258 

Sabin  process 275,  279,  286 

Salmasius 10,  28 

Sandarac 5,  10,  15,  17,  19,  106 

Sand-blast 197 

Sanding 323 

Scraping 195 

Sea-water  tests. 220 


INDEX.  371. 

PAGE 

Shellac 104,  243,  299 

"      white,  insoluble 105 

"      varnish  in  fresh  wafer 243 

Ship  and  boat  painting 297 

Shipping  structural  metal 207 

Ships'-bottom  paints 290,  295 

Shop  marks 206 

Shop  painting  structural  metal 205 

Sienna 131 

Size 8 

Solvents  for  pyroxylin , 114 

Spar  varnish 298 

Spraying  paint 253 

Striping  coat 207 

Substitutes  for  linseed-oil 211 

Surface  of  metal  before  painting 188,  192; 

Table  of  "1896  "  tests 225.- 

"  "  1897-9"  tests 232 

Taylor,  S 347 

Tempera 345, 

Terra  alba 121,  311 

Theophilus n,  12,  22,  333, 

Thinness  of  paint  films 185, 

Thinning  enamel  paint 143 

Thompson,  G.  W 34 

Tingry 2O,  359 

Tingry's  furnace 361 

Tin-plate,  to  paint 321 

Titian 349 

Tripier-Devaux 361 

Tung-oil ...    85,  149 

Turpentine... 7,  95,  133,  312 

oxidation  of 82 

Ultramarine 126 

Umber ; 37,  131 

Vanadium 38 

Van  Eyck 122,  346 

Van  Strij 348 

Varnish,  benzine  in Si 

"        damar 105 

"        definition  of 2 

"        Egyptian 7,  8,  21 

"        enamels 273, 


372  INDEX. 

PAGE 

Varnish,  flowing  of   82 

"        for  steel  structures 246 

"        films,  thickness  of 185,  248 

"        how  made 2,  12,  75 

"        kettle 74 

"        -maker's  furnace  (1778) 358 

"        manufacture  of 71 

"        mixing  of 83 

"        over-cooking 77 

packages 73 

4t        paint 140,  248 

"        remover 326 

"        shellac 104 

"        spirit 103 

"        under-cooking 77 

Vehicle 118 

Venice  turpentine .' 107 

Verenice 28 

Vermilion 15,  126 

Vernice  liquida 9 

Vernis-Martin 332 

Vernix 9,  10 

Violette 361 

Violin  varnish 336 

Vitriol 33 

Vitruvius 26,  333,  340 

Walnut  oil 36 

Water  colors 4 

Water-cooled  mills 135 

Watin 351,  353 

Wax 4,  9.  319.  342 

White  lead 119,  212,  297,  311,  340 

White  under-body ,  value  of 121 

Whiting 121 

White  zinc 120 

Williams,  E.  D 112 

Wire-brushing « 196 

Wood  sheathing  for  ships'-bottoms 291 

Xenophon 302,  340 

Zinc  sulphate 33 

"    white 120 


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oo 
50 

00 
00 

So 


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Vol.  I  .............................................  Large  Svo,   5  oo 

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Short  Course  in  Inorganic  Qualitative  Chemical  Analysis  for  Engineering 

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Whipple's  Microscopy  of  Drinking-water 8vo,  3  50 

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Wulling's  Elementary  Course  in  Inorganic  Pharmaceutical  and  Medical  Chem- 
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BRIDGES  AND    ROOFS.       HYDRAULICS,      MATERIALS    OP    ENGINEERING 
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Bixby's  Graphical  Computing  Table Paper  19$  X  24!  inches.  35 

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Comstock's  Field  Astronomy  for  Engineers 8vo,  a  50 

Davis's  Elevation  and  Stadia  Tables 8vo,  I  oo 

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5 


French  and  Ives's  Stereotomy 8vo,  a  3« 

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Goodrich's  Economic  Disposal  of  Towns'  Refuse 8vo,  3  50 

Gore's  Elements  of  Geodesy , 8vo,  2  50 

Hayford's  Text-book  of  Geodetic  Astronomy 8vo,  3  oo 

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Johnson's  Theory  and  Practice  of  Surveying Small  8vo,  4  oo 

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Elements  of  Sanitary  Engineering 8vo,  a  oo 

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Hugent's  Plane  Surveying  , 8vo,  3  90 

Ogden'f  Sewer  Design izmo,  a  oo 

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Burr's  Course  on  the  Stresses  in  Bridges  and  Roof  Trusses,  Arched  Ribs,  and 

Suspension  Bridges 8vo,  3  50 

Dm  Bois's  Mechanics  of  Engineering.     VoL  II Small  4to,  10  oo 

Foster's  Treatise  on  Wooden  Trestle  Bridges 4to,  5  oo 

Fowler's  Coffer-dam  Process  for  Piers 8vo,  a  50 

OrMne's  Roof  Trusses ". 8vo,  x  as 

Bridge  Trusses 8vo,  a  50 

Arches  in  Wood,  Iron,  and  Stone 8vo,  a  50 

Howe's  Treatise  on  Arches 8vo,  4  oo 

Design  of  Simple  Roof -trusses  in  Wood  and  Steel 8vo,  2  oo 

Johnson,  Bryan,  and  Turneaure's  Theory  and  Practice  in  the  Designing  of 

Modern   Framed   Structures Small  4to,  10  oo 

Merriman  and  Jacoby's  Text-book  on  Roofs  and  Bridges: 

Part  I. — Stresses  in  Simple  Trusses 8vo,  a  50 

Part  II.— Graphic  Statics 8vo,  2  50 

Part  III.— Bridge  Design.     4th  Edition,  Rewritten 8vo,  2  50 

Part  TV.— Higher  Structures 8vo,  2  50 

Morlson's  Memphis  Bridge 4to,  10  oo 

6 


WaddelTs  De  Pontibus,  a  Pocket-book  for  Bridge  Engineers. . .  i6mot  morocco,  3  o« 

Specifications  for  Steel  Bridges i amo,  i  25 

Wood's  Treatise  on  the  Theory  of  the  Construction  of  Bridges  and  Roofs .  8vo,  a  oo 

Wright's  Designing  of  Draw-spans: 

Part  I.  — Plate-girder  Draws 8vo,  a  50 

Part  II. — Riveted-truss  and  Pin-connected  Long-span  Draws 8vo,    a  50 

Two  parts  in  one  Tolume  v, .8vo,  3  50 

HYDRAULICS. 
Barin's  Experiments  upon  the  Contraction  of  the  Liquid  Vein  Issuing  from  an 

Orifice.     (Trautwine.) 8vo,   a  oo 

Bov«y*s  Treatise  on  Hydraulics 8vo,  5  oo 

Church's  Mechanics  of  Engineering 8vo,  6  oo 

Diagrams  of  Mean  Velocity  of  Water  in  Open  Channels paper,  i  50 

Coffin's  Graphical  Solution  of  Hydraulic  Problems i6mo,  morocco,  a  50 

Flather's  Dynamometers,  and  the  Measurement  of  Power zamo,  3  oo 

FolwelTs  Water-supply  Engineering 8vo,  4  oo 

PrizelTs  Water-power 8vo,   5  oo 

Fuertes's  Water  and  Public  Health lamo,  x  50 

Water-filtration  Works xamo,  a  50 

Oanguillet  and  Kutter's  General  Formula  for  the  Uniform  Flow  of  Water  in 

Rivers  and  Other  Channels.     (Hering  and  Trautwine.) 8vo,  4  oo 

Hazen's  Filtration  of  Public  Water-supply 8vo,  3  oo 

Hazlehurst's  Towers  and  Tanks  for  Water- works 8vo,  a  50 

Herschel's  115  Experiments  on  the  Carrying  Capacity  of  Large,  Riveted,  Metal 

Conduits 8vo,  a  oo 

Mason's   Water-supply.     (Considered   Principally   from   a   Sanitary   Stand- 
point.)   3d  Edition,  Rewritten 8vo,  4  oo 

Merriman's  Treatise  on  Hydraulics.     9th  Edition,  Rewritten 8vo,  5  oo 

*  Michie's  Elements  of  Analytical  Mechanics 8ro,  4  oo 

Schuyler's  Reservoirs  for  Irrigation,  Water-power,  and  Domestic  Water- 
supply Large  8vo,  5  oo 

**  Thomas  and  Watt's  Improvement  of  Riyers.     (Post.,  44  c.  additional),  4to,  6  oo 

Turneaure  and  Russell's  Public  Water-supplies 8vo,  5  oo 

Wegmann's  Desiam  and  Construction  of  Dams .' 4to,  5  oo 

Water-supply  of  the  City  of  New  York  from  1658  to'iSos 4to,  10  oo 

Weisbach's  Hydraulics  and  Hydraulic  Motors.     (Du  Bois.) 8vo,  5  oo 

Wilson's  Manual  of  Irrigation  Engineering Small  8vo.  4  oo 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  3  oo 

Wood's  Turbines 8vo,  a  50 

Elements  of  Analytical  Mechanics 8vo,  3  oo 

MATERIALS  OP  ENGINEERING. 

Baker's  Treatise  on  Masonry  Construction 8vo,  5  oo 

Roads  and  Pavements 8vo,  5  oo 

Black's  United  States  Public  Works Oblong  4to,  5  oo 

Bovey's  Strength  of  Materials  and  Theory  of  Structures 8vo,  7  50 

Burr's  Elasticity  and  Resistance  of  the  Materials  of  Engineering.     6th  Edi- 
tion, Rewritten 8vo,  7  50 

Byrne's  Highway  Construction '.8vo,  5  oo 

Inspection  of  the  Materials  and  Workmanship  Employed  .in  Construction. 

i6mo,  3  oo 

Church's  Mechanics  of  Engineering 8vo,  6  oo' 

Du  Bois's  Mechanics  of  Engineering.     VoL  I Small  4to,  7  50 

Johnson's  Materials  of  Construction Large  8vo,  6  oo 

Keep's  Cast  Iron 8vo,  a  50 

Lanza's  Applied  Mechanics 8vo,  7  50 

Martens's  Handbook  on  Testing  Materials.     (Henning.)     a  vols 8vo,  7  50 

Merrill's  Stones  for  Building  and  Decoration 8vo,  5  oo 

7 


Meniman's  Text-book  on  the  Mechanics  of  Materials 8vo,  4  oo 

Strength  of  Materials i2mo,  i  oo 

Metcalf 's  SteeL    A  Manual  for  Steel-users lamo,  2  oo 

Patton's  Practical  Treatise  on  Foundations 8vo,  5  oo 

Richey's  Hanbbook  for  Building  Superintendents  of  Construction.     (In  press. ) 

Rockwell's  Roads  and  Pavements  in  France I2mo,  i  25 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish 8vo,  3  oo 

Smith's  Materials  of  Machines i2mo,  i  oo 

Snow's  Principal  Species  of  Wood 8vo,  3  50 

Spalding's  Hydraulic  Cement izmo,  2  oo 

Text-book  on  Roads  and  Pavements i2mo,  2  oo 

Taylor  and  Thompson's  Treatise  on  Concrete,  Plain  and  Reinforced.      (In 
press.) 

Thurston's  Materials  of  Engineering.     3  Parts 8vo,  8  oo 

Part  I. — Non-metallic  Materials  of  Engineering  and  Metallurgy 8vo,  2  oo 

Part  H.— Iron  and  Steel 8vo,  3  50 

Part  in. — A  Treatise  on  Brasses,  Bronzes,  and  Other  Alloys  and  their 

Constituents 8vo,  2  50 

Thurston's  Text-book  of  the  Materials  of  Construction 8vo,  5  oo 

Tillson's  Street  Pavements  and  Paving  Materials 8vo,  4  oo 

Waddell's  De  Pontibus.     (A  Pocket-book  for  Bridge  Engineers.) . .  i6mo,  mor.,  3  oo 

Specifications  for  Steel  Bridges i2mo,  i  as 

Wood's  Treatise  on  the  Resistance  of  Materials,  and  an  Appendix  on  the  Pres- 
ervation of  Timber 8vo,  2  oo 

Elements  of  Analytical  Mechanics 8vo,  3  oo 

Wood's  Rustless  Coatings:  Corrosion  and  Electrolysis  of  Iron  and  Steel. .  .8vo,  4  oo 

RAILWAY  ENGINEERING. 

Andre ws's  Handbook  for  Street  Railway  Engineers.     3X5  inches,  morocco,  i  25 

Berg's  Buildings  and  Structures  of  American  Railroads 4to,  5  oo 

Brooks's  Handbook  of  Street  Railroad  Location i6mo.  morocco,  i  50 

Butts's  Civil  Engineer's  Field-book i6mo,  morocco,  2  50 

Crandall's  Transition  Curve x6mo,  morocco,  i  50 

Railway  and  Other  Earthwork  Tables 8vo,  i  50 

Dawson's  "Engineering"  and  Electric  Traction  Pocket-book.    i6mo,  morocco,  5  oo 

Dredge's  History  of  the  Pennsylvania  Railroad:   (1879) Paper,  5  oo 

*  Drinker's  Tunneling,  Explosive  Compounds,  and  Rock  Drills,  4to,  half  mor.,    25  oo 

Fisher's  Table  of  Cubic  Yards Cardboard,  25 

Godwin's  Railroad  Engineers'  Field-book  and  Explorers'  Guide 1 6mo,  mor.,  2  50 

Howard's  Transition  Curve  Field-book i6mo,  morocco,  i  50 

Hudson's  Tables  for  Calculating  the  Cubic  Contents  of  Excavations  and  Em- 
bankments    8vo,  i  oo 

Molitor  and  Beard's  Manual  for  Resident  Engineers i6mo,  i  oo 

Nagle's  Field  Manual  for  Railroad  Engineers i6mo,  morocco.  3  oo 

Philbrick's  Field  Manual  for  Engineers i6mo,  morocco,  3  oo 

Searles's  Field  Engineering i6mo,  morocco,  3  oo 

Railroad  Spiral. i6mo,  morocco,  i  50 

Taylor's  Prismoidal  Formula  and  Earthwork 8vo,  i  50 

•  Trautwine's  Method  of  Calculating  the  Cubic  Contents  of  Excavations  and 

Embankments  by  the  Aid  of  Diagrams 8vo,  2  oo 

The  Field  Practice  of  [Laying    Out    Circular    Curves   for    Railroads. 

1 2 mo,  morocco,  2  50 

Cross-section  Sheet Paper,  25 

Webb's  Railroad  Construction.     2d  Edition,  Rewritten i6mo.  morocco,  s  oo 

Wellington's  Economic  Theory  of  the  Location  of  Railways Small  8vo,  5  oo 

DRAWING. 

Barr's  Kinematics  of  Machinery 8vo,  2  50 

*  Bartlett's  Mechanical  Drawing -. 8vo,  3  oo 

•  "        Abridged  Ed 8vo,  i  50 


Coolidge's  Manual  of  Drawing 8vo,  paper,  i  oo 

Coolidge  and  Freeman's  Elements  of  General  Drafting  for  Mechanical  Engi- 
neers.    (In  press.) 

Durley's  Kinematics  of  Machines 8vo,  4  oo 

Hill's  Text-book  on  Shades  and  Shadows,  and  Perspective 8vo,  2  oo 

Jamison's  Elements  of  Mechanical  Drawing.     (In  press.) 
Jones's  Machine  Design: 

Part  I. — Kinematics  of  Machinery 8vof  i  50 

Part  n. — Form,  Strength,  and  Proportions  of  Parts 8vo,  3  oo 

MacCord's  Elements  of  Descriptive  Geometr}              ,      8vo,  300 

Kinematics;  or.  Practical  Mechanism 8vo,  5  oo 

Mechanical  Drawing 4to,  4  oo 

Velocity  Diagrams 8vo,  i  50 

*  Mahan's  Descriptive  Geometry  and  Stone-cutting 8vo,  i  50 

Industrial  Drawing.    (Thompson.) 8vo,  3  50 

Mover's  Descriptive  Geometry.    (In  press.) 

Reed's  Topographical  Drawing  and  Sketching 4to,  5  oo 

Reid's  Course  in  Mechanical  Drawing 8vo,  2  oo 

Text-book  of  Mechanical  Drawing  and  Elementary  Machine  Design.  .8vo,  3  oo 

Robinson's  Principles  of  Mechanism 8vo,  3  oo 

Smith's  Manual  of  Topographical  Drawing.     (McMillan.) 8vo,  a  50 

Warren's  Elements  of  Plane  and  Solid  Free-hand  Geometrical  Drawing. .  I2mo,  x  oo 

Drafting  Instruments  and  Operations 12010,  x  25 

Manual  of  Elementary  Projection  Drawing I2mo,  i  50 

Manual  of  Elementary  Problems  in  the  Linear  Perspective  of  Form  and  a 

Shadow i2mo,  x  oo 

Plane  Problems  in  Elementary  Geometry i2mo,  x  25 

Primary  Geometry i2mo,  75 

Elements  of  Descriptive  Geometry,  Shadows,  and  Perspective 8vo,  3  50 

General  Problems  of  Shades  and  Shadows 8vo,  3  oo 

Elements  of  Machine  Construction  and  Drawing 8vo,  7  So 

Problems.  Theorems,  and  Examples  in  Descriptive  Geometry 8vo,  2  50 

Weisbach's  Kinematics  and  the  Power  of  Transmission.       (Hermann  and 

Klein.)  ; . . .  8vo,  5  oo 

Whelp  ley's  Practical  Instruction  In  the  Art  of  Letter  Engraving 12  mo,  2  oo 

Wilson's  Topographic  Surveying 8vo,  3  50 

Free-hand  Perspective 8vo,  2  50 

Free-hand  Lettering 8vo,  x  oo 

Woolf 's  Elementary  Course  in  Descriptive  Geometry Large  8vo,  3  oo 

ELECTRICITY  AND  PHYSICS. 

Anthony  and  Brackett's  Text-book  of  Physics.     (Magie.) Small  8vo,  3  oo 

Anthony's  Lecture-notes  on  the  Theory  of  Electrical  Measurements 12 mo,  i  oo 

Benjamin's  History  of  Electricity 8vo,  3  oo 

Voltaic  CelL 8vo,  3  oo 

Classen's  Quantitative  Chemical  Analysis  by  Electrolysis.    (Boltwood.).  .8vo,  3  oo 

Crehore  and  Sauier's  Polarizing  Photo-chronograph 8vo,  3  oo 

Dawson's  "Eneineering"  and  Electric  Traction  Pocket-book.  .i6mo,  morocco,  5  oo 
Dolezalek's   Theory  of   the   Lead   Accumulator    (Storage    Battery).     (Von 

Ende.) izmo,  *  2  50 

Duhem's  Thermodynamics  and  Chemistry.     (Burgess.) 8vo,  4  oo 

Flather's  Dynamometers,  and  the  Measurement  of  Power I2mo,  3  oo 

Gilbert's  De  Magnete.     (Mottelay.) 8vo,  2  50 

Hanchett's  Alternating  Currents  Explained 12 mo,  i  oo 

Bering's  Ready  Reference  Tables  (Conversion  Factors) i6mo,  morocco,  2  50 

Holman's  Precision  of  Measurements 8vo,  2  oo 

Telescopic  Mirror-scale  Method,  Adjustments,  and  Tests. Large  8vo,  75 

9 


Landauer's  Spectrum  Analysis.    (Tingle.)  ............................  8vo,  3  <>• 

Le  Chatelier's  High-temperature  Measurements.  (Boudouard  —  iJurgess.)i2mc,  3  oo 

Lob's  Electrolysis  and  Electrosynthesis  of  Organic  Compounds.  (Lorenz.)  i  zmo,  i  oo 

*  Lyons's  Treatise  on  Electromagnetic  Phenomena.    Vols.I.and  IL  8vo,  each,  6  oo 

*  Michie.     Elements  of  Wave  Motion  Relating  to  Sound  and  Light  .......  8vo,  4  oo 

Niaudet's  Elementary  Treatise  on  Electric  Batteries.     (Fishoack.  )  ......  i  amo,  50 

*  Rosenberg's  Electrical  Engineering.   (Haldane  Gee—  Kinzbrunner.)  ----  8vo,  50 

Ryan,  Norris,  and  Hozie's  Electrical  Machinery.    Vol.  L  ...............  8vo,  9* 

Thurston's  Stationary  Steam-engines  ...............................  8vo,  50 

*  TUlman's  Elementary  Lessons  in  Heat  ..............................  8vo,  90 

Tory  and  Pitcher's  Manual  of  Laboratory  Physics  ..............  Small  8vo,  oo 

Hike's  Modern  Electrolytic  Copper  Refining  .......................  8vo,  3  oo 

LAW. 

*  Davis's  Elements  of  Law  ........................................  8vo,    2  50 

*  Treatise  on  the  Military  Law  of  United  States  ...................  8vo,    7  oo 

Sheep,  7  So 

Manual  for  Courts-martial  ..............................  i6mo,  morocco,  i  50 

Wait's  Engineering  and  Architectural  Jurisprudence  ...................  8vo,  6  oo 

Sheep,  6  50 
Law  of  Operations  Preliminary  to  Construction  in  Engineering  and  Archi- 

tecture ................................................    8vo,  5  o« 

Sheep,  5  SO 

Law  of  Contracts  .............................................  8vo,  3  oo 

Winthrop's  Abridgment  of  Military  Law  ............................  i2mo,  2  5* 

MANUFACTURES. 

Bernadou's  Smokeless  Powder  —  Nitro-cellulose  and  Theory  of  the  Cellulose 

Molecule  ..............................................  I2mo,  2  5« 

Holland's  Iron  Founder  .........................................  izmo,  2  50 

"  The  Iron  Founder,**  Supplement  ...........................  i2mo,  2  50 

Encyclopedia  of  Founding  and  Dictionary  of  Foundry  Terms  Used  in  the 

Practice  of  Moulding  ....................................  izmo,  3  oo 

Eissler's  Modern  High  Explosives  ...................................  8vo,  4  oo 

Effront's  Enzymes  and  their  Applications.     (Prescott.)  .................  8vo,  3  oo 

Fitzgerald's  Boston  Machinist  ....................................  i8mo,  z  oo 

Ford's  Boiler  Making  for  Boiler  Makers  ............................  i8mo,  i  oe 

Hopkins's  Oil-chemists'  Handbook  .................................  8vo,  3  oo 

Keep's  Cast  Iron  .................................................  8vo,  2  50 

Leach's  The  Inspection  and  Analysis  of  Food  with  Special  Reference  to  State 

Control.     (In  preparation.) 
Matthews's  The  Textile  Fibres.    (7n  press.) 

Metcalf's  Steel.     A  Manual  for  Steel-users  .........................  ismo,  2  o* 

Metcalfe's  Cost  of  Manufactures  —  And  the  Administration    of  Workshops, 

Public  and  Private  .......................................  8vo,  5  oo 

Meyer's  Modern  Locomotive  Construction  ............................  4to,  10  oo 

Morse's  Calculations  used  in  Cane-sugar  Factories  ..........  i6mo,  morocco,  i  50 

*  Reisig's  Guide  to  Piece-dyeing  ...................................  8vo,  25  oo 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish  ......  8vo,  3  oo 

Smith's  Press-working  of  Metals  ....................................  8vo,  3  oo 

Spalding's  Hydraulic  Cement  .....................................  i  ?.mo,  2  oo 

Spencer's  Handbook  for  Chemists  of  Beet-sugar  Houses  .....  i6mo,  morocco,  3  oo 

Handbook  tor  sugar  Manufacturers  ana  their  Chemists.  .  .  z6mo,  morocco,    2  oo 
Taylor  and  Thompson's  Treatise  on  Concrete,  Plain  and  Reinforced.    (In 


Thonton's  Manual  of  Steam-boilers,  their  Designs,  Construction  and  Opera- 

tion ...................................................  8vo,    5  oo 

10 


*  Walke'v  Lectures  on  Explosive* 8vo,  4  oo 

West's  American  Foundry  Practice i2mo,  2  50 

Moulder's  Text-book X2mo,  2  50 

Wiechmann's  Sugar  Analysis Small  8vo,  2  50 

Wol£f's  Windmill  as  a  Prime  Mover 8vo,  3  oo  • 

Woodbury's  Fire  Protection  of  Mills 8vo,  2  50 

Wood's  Rustless  Coatings:  Corrosion  and  Electrolysis  of  Iron  and  Steel. .  .8vo,  4  oo 

MATHEMATICS. 

Baker's  Elliptic  Functions 8vo,  x  5« 

*  Bass's  Elements  of  Differential  Calculus I2mo,  4  o* 

Briggs's  Elements  of  Plane  Analytic  Geometry.  / X2mo,  I  oo 

Compton's  Manual  of  Logarithmic  Computations i2mo,  x  50 

Davis's  Introduction  to  the  Logic  of  Algebra 8vo,  x  50 

*  Dickson's  College  Algebra Large  I2mo,  x  SO 

*  Answers  to  Dickson's  College  Algebra 8vo,  paper,       as 

*  Introduction  to  the  Theory  of  Algebraic  Equations   Large  12 mo,    x  25 

Halsted's  Elements  of  Geometry 8vo,    x  75 

Elementary  Synthetic  Geometry 8vo,  x  50 

Rational  Geometry I2mo( 

•Johnson's  Three-place  Logarithmic  Tables:    Vest-pocket  size paper,  15 

100  copies  for  5  oo 

*  Mounted  on  heavy  cardboard,  8  X 10  inches,  as 

xo  copies  for  a  oo 

Elementary  Treatise  on  the  Integral  Calculus Small  8vo,  x  50 

Curve  Tracing  in  Cartesian  Co-ordinates i2mo,  x  oo 

Treatise  on  Ordinary  and  Partial  Differential  Equations. ....  .Small  8vo,  3  50 

Theory  of  Errors  and  the  Method  of  Least  Squares xamo,  x  so 

*  Theoretical  Mechanics ramo,  3  oo 

Laplace's  Philosophical  Essay  on  Probabilities.     (Truscott  and  Emory.)  i2mo,  200 

*  Ludlow  and  Bass.     Elements  of  Trigonometry  and  Logarithmic  and  Other 

Tables 8vo,  3  oo 

Trigonometry  and  Tables  published  separately Each,  a  oo 

*  Lud low's  Logarithmic  and  Trigonometric  Tables 8vo,  x  oo 

Maurer's  Technical  Mechanics 8vo,  4  oo 

Merriman  and  Woodward's  Higher  Mathematics 8vo,  5  oo 

Merriman's  Method  of  Least  Squares 8vo,  2  oo 

Rice  and  Johnson's  Elementary  Treatise  on  the  Differential  Calculus .  Sm.,  8vo,  3  oo 

Differential  and  Integral  Calculus.  2  vols.  in  one Small  8vo,  2  50 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish 8vo,  3  oo 

Wood's  Elements  of  Co-ordinate  Geometry 8vo,  a  oo 

Trigonometry:  Analytical,  Plane,  and  Spherical xamo,  x  oo 

MECHANICAL   ENGINEERING. 

MATERIALS  OF  ENGINEERING,  STEAM-ENGINES  AND  BOILERS. 

Bacon's  Forge  Practice xamo,  x  50 

Baldwin's  Steam  Heating  for  Buildings xamo,  2  50 

Barr's  Kinematics  of  Machinery 8vo,  2  50 

*  Bartlett's  Mechanical  Drawing 8vo,  3  oo 

'«  "        Abridged  Ed 8vor  x  s* 

Benjamin's  Wrinkles  and  Recipes izmo,  2  oo 

Carpenter's  Experimental  Engineering 8vo,  6  oo 

Heating  and  Ventilating  Buildings 8vo,  4  oo 

Gary's  Smoke  Suppression  in  Plants  using  Bituminous  CoaL     (In  prep- 
aration.) 

Clerk's  Gas  and  Oil  Engine Small  8vo,  4  oo 

Coolidge's  Manual  of  Drawing 8vo,    paper,  x  oo 

11 


Coolidge  and  Freeman's  Elements  of  General  Drafting  for  Mechanical  En- 
gineers.    (/TJ  press.) 

Cromwell's  Treatise  on  Toothed  Gearing i2mo,  I  50 

Treatise  on  Belts  and  Pulleys I2mo,  i  50 

Barley's  Kinematics  of  Machines 8vo,  4  <x> 

Flather's  Dynamometers  and  the  Measurement  of  Power i2mo,  3  oo 

Rope  Driving I2mo,  2  oo 

Gill's  Gas  and  Fuel  Analysis  for  Engineers „ , i2mo,  i  25 

Hall's  Car  Lubrication i2mo,  i  oo 

Bering's  Ready  Reference  Tables  (Conversion  Factors) i6mo,  morocco,  2  50 

Button's  The  Gas  Engine 8vo,  5  oo 

Jones's  Machine  Design: 

Part  I. — Kinematics  of  Machinery Svo,  i  50 

Part  IL — Form,  Strength,  and  Proportions  of  Parts 8vo,  3  oo 

Kent's  Mechanical  Engineer's  Pocket-book i6mo,   morocco,  5  oo 

Kerr's  Power  and  Power  Transmission 8vo,  2  oo 

Leonard's  Machine  Shops,  Tools,  and  Methods.    (In  preta.) 

MacCprd's  Kinematics;  or,  Practical  Mechanism 8vo,  5  oo 

Mechanical  Drawing 4to,  4  oo 

Velocity  Diagrams 8vo,  i  50 

Mahan's  Industrial  Drawing.    (Thompson.) 8vo,  3  50 

Poole's  Calorific  Power  of  Fuels 8vo,  3  oo 

Reid's  Course  in  Mechanical  Drawing 8vo.  2  oo 

Text-book  of  Mechanical  Drawing  and  Elementary  Machine  Design.  .8vo,  3  oo 

Richards's  Compressed  Air xamo,  i  50 

Robinson's  Principles  of  Mechanism 8vo,  3  oo 

Schwamb  and  Merrill's  Elements  of  Mechanism.     (In  press.) 

Smith's  Press-working  of  Metals   8vo,  3  oo 

Thurston's  Treatise  on    Friction   and    Lost  Work   in    Machinery   and   Mill 

Work 8vo,  300 

Animal  as  a  Machine  and  Prime  Motor,  and  the  Laws  of  Energetics .  i2mo,  i  oo 

Warren's  Elements  of  Machine  Construction  and  Drawing 870,  7  50 

Weisbach's  Kinematics  and  the  Power  of  Transmission.      Herrmann — 

Klein.) 8vo,  5  oo 

Machinery  of  Transmission  and  Governors.     (Herrmann — Klein. ).  .8vo,  5  oo 

HydrauLcs  and  Hydraulic  Motors.     (Du  Bois.) 8vo,  5  oo 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  3  oo 

Wood's  Turbines   .8vo,  a  50 

MATERIALS  OF  ENGINEERING. 

Bovey's  Strength  of  Materials  and  Theory  of  Structures 8vo,  7  50 

Burr's  Elasticity  and  Resistance  of  the  Materials  of  Engineering.     6th  Edition, 

Reset 8vo,  7  50 

Church's  Mechanics  of  Engineering 8vo,  6  oo 

Johnson'"  Materials  of  Construction Large  Svo,  6  oo 

Keep's  Cast  Iron Svo,  2  50 

Lanza's  Applied  Mechanics 8vo,  7  5<> 

Martens's  Handbook  on  Testing  Materials.     (Henning.) 8vo,  7  50 

Merriman's  Tert-book  on  the  Mechanic*  of  Materials 8vo,  4  oo 

Strength  of  Materials i2mo,  i  oo 

Metcalf's  SteeL     A  Manual  for  Steel-users i2mo,  2  oo 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish Svo,  3  oo 

Smith's  Materials  of  Machines iamo,  i  oo 

Thurston's  Materials  of  Engineering 3  vols  ,  Svo,  8  oo 

Part  II.— Iron  and  Steel Svo,  3  50 

Part  III. — A  Treatise  on  Brasses,  Bronzes,  and  Other  Alloys  and  their 

Constituents. Svo  2  50 

Text-book  of  the  Materials  of  Construction Svo,  5  oo 

12 


Wood's  Treatise  on  the  Resistance  of  Materials  and  an  Appendix  on  the 

Preservation  of  Timber 8vo,  a  oo 

Elements  of  Analytical  Mechanics 8vo,  3  oo 

Wood's  Rustless  Coatings:  Corrosion  and  Electrolysis  of  Iron  and  Steel. .  ,8vo,  4  oo 

STEAM-ENGINES  AND  BOILERS. 

Carnot's  Reflections  on  the  Motive  Power  of  Heat.     (Thurston.) i2mo,  i  50 

Dawson's  "Engineering"  and  Electric  Traction  Pocket-book. .  t6mo,  mor.,  5  oo 

Ford's  Boiler  Making  for  Boiler  Makers x8mo,  i  oo 

Goss's  Locomotive  Sparks 8vo,  a  oo 

Hemen way's  Indicator  Practice  and  Steam-engine  Economy 12 mo,  a  oo 

Button's  Mechanical  Engineering  of  Power  Plants 8vo,  5  oo 

Heat  and  Heat-engines 8vo,  5  oo 

Kent's  Steam-bo'ler  Economy 8vo,  4  oo 

Kneass's  Practice  and  Theory  of  the  Injector 8vo  i  50 

MacCord's  Slide-valves 8vo,  a  oo 

Meyer's  Modern  Locomotive  Construction 4to,  zo  oo 

Peabody's  Manual  of  the  Steam-engine  Indicator zamo,  z  50 

Tables  of  the  Properties  of  Saturated  Steam  and  Other  Vapors 8vo,  z  oo 

Thermodynamics  of  the  Steam-engine  and  Other  Heat-engines 8vo,  5  oo 

Valve-gears  for  Steam-engines 8vo,  a  50 

Peabody  and  Miller's  Steam-boilers 8vo,  4  oo 

Pray*s  Twenty  Years  with  the  Indicator Large  8vo,  a  50 

Pupln's  Thermodynamics  of  Reversible  Cycles  in  Gases  and  Saturated  Vapors. 

(Osterberg.) zamo,  z  as 

Reagan's  Locomotives :  Simple,  Compound,  and  Electric zamo,  a  50 

Rontgen's  Principles  of  Thermodynamics.     (Du  Bois.) 8vo,  5  oo 

Sinclair's  Locomotive  Engine  Running  and  Management zamo,  a  oo 

Smart's  Handbook  of  Engineering  Laboratory  Practice zamo,  a  50 

Snow's  Steam-boiler  Practice 8vo,  3  oo 

Spangler's  Valve-gears 8vo,  a  50 

Notes  on  Thermodynamics i amo,  z  oo 

Spangler,  Greene,  and  Marshall's  Elements  of  Steam-engineering 8vo,  3  oo 

Thurston's  Handy  Tables 8vo,  z   50 

Manual  of  the  Steam-engine a  vols.  8vo,  zo  oo 

Part  I. — History.  Structuce,  and  Theory 8vo,  6  oo 

Part  II. — Design,  Construction,  and  Operation 8vo,  6  oo 

Handbook  of  Engine  and  Boiler  Trials,  and  the  Use  of  the  Indicator  and 

the  Prony  Brake 8vo  5  oo 

Stationary  Steam-engines 8vo,  a  50 

Steam-boiler  Explosions  in  Theory  and  in  Practice zamo  z  50 

Manual  of  Steam-boilers ,  Their  Designs,  Construction,  and  Operation .  8vo ,  5  oo 

Weisbach's  Heat,  Steam,  and  Steam-engines.     (Du  Bois.) 8vo,  5  oo 

Whitham's  Steam-engine  Design 8vo,  5  oo 

Wilson's  Treatise  on  Steam-boilers.     (Flather.) z6mo,  a  50 

Wood's  Thermodynamics  Heat  Motors,  and  Refrigerating  Machines 8vo,  4  oo 


MECHANICS    AND  MACHINERY. 

Barr's  Kinematics  of  Machinery 8vo,  a  50 

Bovey's  Strength  of  Materials  and  Theory  of  Structures 8vo,  7  50 

Chase's  The  Art  of  Pattern-making zamo,  a  50 

ChordaL— Extracts  from  Letters zamo,  a  oo 

Church's  Mechanics  of  Engineering 8vo,  6  oo 

Notes  and  Examples  in  Mechanics 8vo,  a  oo 

13 


Compton's  First  Lesson*  in  Metal-working iamo,    i  50 

Compton  and  De  Groodt's  The  Speed  Lathe iamo,    i  50 

Cromwell's  Treatise  on  Toothed  Gearing xamo,    x  50 

Treatise  on  Belts  and  Pulleys iamo,    i  50 

Dana's  Text-book  of  Elementary  Mechanics  for  the  Use  of  Colleges  and 

Schools iamo,    i  50 

Dingey's  Machinery  Pattern  Making iamo,    a  oo 

Dredge's  Record  of  the  Transportation  Exhibits   Building  of  the  World's 

Columbian  Exposition  of  1893 4to,  half  morocco,    5  oo 

Du  Boit's  Elementary  Principles  of  Mechanics : 

Vol.     I.— Kinematic! 8vo,    3  50 

Vol.   n. — Statics 8vo,    4  oo 

Vol.  HI. — Kinetic* 8vo,    3  50 

Mechanics  of  Engineering.     VoL  I Small  4to,     7  50 

VoL  IL Small  4to,    10  oo 

Durley'*  Kinematics  of  Machines  8vot    4  oo 

Fitzgerald's  Boston  Machinist i6mo,    x  oo 

Flather's  Dynamometers,  and  the  Measurement  of  Power xamo,    3  oo 

Rope  Driving xamo,    a  oo 

Go**'*  Locomotive  Spark* Svo  a  oo 

Hall's  Car  Lubrication xamo,    x  oo 

Holly**  Art  of  Saw  Filing iSmo         75 

•  Johnson's  Theoretical  Mechanic* xamo,    3  oo 

Statics  by  Graphic  and  Algebraic  Method* Svo,    a  oo 

Jones'*  Machine  Design: 

Part  I. — Kinematic*  of  Machinery Svo,    x  50 

Part  IL — Form,  Strength,  and  Proportion*  of  Part* Svo,    3  oo 

Ken's  Power  and  Power  Transmission Svo,    a  oo 

Lanza's  Applied  Mechanic* Svo,    7  50 

Leonard  s  Machine  Shops,  Tools,  and  Method*.    (In  press.) 

MacCord's  Kinematic*;  or,  Practical  Mechanism Svo,    5  oo 

Velocity  Diagram* Svo,    x  30 

Maurer's  Technical  Mechanics Svo,   4  oo 

Mtrriman'i  Text-book  on  the  Mechanics  of  Material* 8vo,   4  oo 

*  Michie'*  Elements  of  Analytical  Mechanic* 8vo(   4  oo 

Reagan's  Locomotive*:  Simple,  Compound,  and  Electric iamo,   a  50 

Reid's  Course  in  Mechanical  Drawing Svo,   a  oo 

Text-book  of  Mechanical  Drawing  and  Elementary  Machine  Design . .  Svo,   3  oo 

Richards's  Compressed  Air iamo,    x  50 

Robinson's  Principles  of  Mechanism Svo,    3  oo 

Ryan,  Norris,  and  Hoxie's  Electrical  Machinery.     Vol.1 Svo,   a  s* 

Schwamb  and  Merrill's  Elements  of  Mechanism.     (In  press.) 

Sinclair's  Locomotive-engine  Running  and  Management xamo,    a  oo 

Smith's  Press-working  of  Metals Svo,   3  oo 

Materials  of  Machines iamo,    x  oo 

Spangler,  Greene,  and  Marshall's  Elements  of  Steam-engineering Svo,   3  oo 

Thurston's  Treatise  on  Friction  and  Lost  Work  in  Machinery  and  Mill 

Work Svo,   3  oo 

Animal  as  a  Machine  and  Prime  Motor,  and  the  Law*  of  Energetic* .  xamo,    x  oo 

Warren'*  Element*  of  Machine  Construction  and  Drawing Svo,   7  50 

Weisbach's    Kinematic*    and    the  Power  of    Transmission.     (Herrmann — 

Klein.) Svo,    5  oo 

Machinery  of  Transmission  and  Governors.     (Herrmann — Klein.). Svo,    5  oo 
Wood's  Elements  of  Analytical  Mechanics Svo,   3  oo 

Principles  of  Elementary  Mechanics iamo,    x  as 

Turbines Svo,    a  50 

The  World's  Columbian  Exposition  of  1893 4to,    i  oo 

14 


METALLURGY. 

Bgleston's  Metallurgy  of  Silver,  Gold,  and  Mercury: 

VoL   I.—  Silver  ..............................................  8vo,  7  So 

VoL   II.—  Gold  and  Mercury  ...................................  8vo,  7  So 

**  Iles's  Lead-smelting.     (Postage  9  cents  additional.)  .............  lamo,  50 

Keep's  Cast  Iron  .................................................  8vo,  50 

Kunhardt's  Practice  of  Ore  Dressing  in  Europe  ......................  8vo,  50 

Le  Chatelier's  High-temperature  Measurements.  (Boudouard  —  Burgess.)  .  lamo,     oo 

Metcalf's  Steel.     A  Manual  for  Steel-users  ...................  .  ......  iamo,  oo 

Smith's  Materials  of  Machines  ....................................  xamo,  oo 

Thurston's  Materials  of  Engineering.    In  Three  Parts  ................  8vo,  8  oo 

Part  II.—  Iron  and  Steel  ................  <.  .............  ........  8vo,  3  So 

Part  III.  —  A  Treatise  on  Brasses,  Bronzes,  and  Other  Alloys  and  their 

Constituents  ..............................  .  ............  8vo,  a  50 

Hike's  Modern  Electrolytic  Copper  Refining  ..........................  8vo,  3  oo 

MINERALOGY. 

Barringer's  Description  of  Minerals  of  Commercial  Value.     Oblong,  morocco,  a  50 

Boyd's  Resources  of  Southwest  Virginia  .............................  8vo,  3  oo 

Map  of  Southwest  Virginia  .............  ,  ...........  Pocket-book  form,  a  oo 

Brush's  Manual  of  Determinative  Mineralogy.     (Penfield.)  ............  8ro,  4  oo 

Chester's  Catalogue  of  Minerals  ..............................  8ro,  paper,  x  oo 

Cloth,  x  as 

Dictionary  of  the  Names  of  Minerals  ............................  8vo,  3  50 

Dana's  System  of  Mineralogy  .....................  Large  8vo,  half  leather,  xa  50 

First  Appendix  to  Dana's  New  "System  of  Mineralogy."  ----  Large  8  vo,  i  oo 

Text-book  of  Mineralogy  ......................................  8vo,  4  oo 

Minerals  and  How  to  Study  Them  ............................  lamo,  50 

Catalogue  of  American  Localities  of  Minerals  ..............  Large  8vo,  oo 

Manual  of  Mineralogy  and  Petrography  .............    .........  xamo,  oo 

Eakle's  Mineral  Tables  ............................................  8vo,  as 

Egleston's  Catalogue  of  Minerals  and  Synonyms  ......................  8vo,  so 

Hussak's  The  Determination  of  Rock-forming  Minerals.     (Smith.)  Small  8vo,  oo 

Merrill's  Non-metallic  Minerals:  Their  Occurrence  and  Uses.  ............  8vo,  4  oo 

*  Penfield's  Notes  on  Determinative  Mineralogy  and  Record  of  Mineral  Tests. 

8ro,  paper,  o  50 
Rotenbusch's   Microscopical  Physiography  of   the   Rock-making   Minerals. 

(Iddings.)  ...............................................  8vo,  5  oo 

*  TiUman's  Text-book  of  Important  Minerals  and  Docks  ...............  8ro,  a  oo 

Williams's  Manual  of  Lithology  ....................................  8vo,  3  oo 

MINING. 

Beard's  Ventilation  of  Mines  .....................................  xamo,  a  50 

Boyd's  Resources  of  Southwest  Virginia  .............................  8vo,  3  oo 

Map  of  Southwest  Virginia  ........................  Pocket-book  form,  a  »oo 

*  Drinker's  Tunneling,  Explosive  Compounds,  and  Rock  Drills. 

4to,  half  morocco,  as  oo 

Bissler's  Modern  High  Explosives  ....................  „  .............  8vo,  4  oo 

Fowler's  Sewage  Works  Analyses  .................................  xamo, 

Goodyear's  Coal-mines  of  the  Western  Coast  of  the  United  States  ......  xamo, 

Ihlseng's  Manual  of  Mining  .......................................  8vo, 

**  Iles's  Lead-smelting.     (Postage  gc.  additional.)  ..................  xamo, 

Kunhardt's  Practice  of  Ore  Dressing  in  Europe  .......................  8vo, 

O'Driscoll's  Notes  on  the  Treatment  of  Gold  Ores  .....................  8vo, 

*  Walke's  Lectures  on  Explosives  ..................................  8vo, 

Wilson's  Cyanide  Processes  ......................................  xamo, 


Chlorination  Process  ........................................  xamo, 

Hydraulic  and  Placer  Mining  .................................  xamo, 

Treatise  on  Practical  and  Theoretical  Mine  Ventilation  ...........  xamo 

15 


oo 
50 
oo 
50 
50 
oo 
oo 
50 
30 
oo 
as 


SANITARY  SCIENCE. 

Cope  land' «  Manual  of  Bacteriology.     (In  preparation.) 

FolwelTs  Sewerage.     (Designing,  Construction  and  Maintenance.) Svo,  3  oo 

Water-supply  Engineering 8vo,  4  oo 

Fuertes's  Water  and  Public  Health xamo,  z  50 

Water-filtration   Works xamo,  2  50 

Gerhard's  Guide  to  Sanitary  House-inspection i6mo,  i  oo 

Goodrich's  Economical  Disposal  of  Town's  Refuse Demy  8vo,  3  5* 

Hazen's  Filtration  of  Public  Water-supplies 8vo,  3  oo 

Kiersted's  Sewage  Disposal iamo,  i  25 

Leach's  The  Inspection  and  Analysis  of  Food  with  Special  Reference  to  State 

Control.     (In  preparation.) 

Mason's    Water-supply.     (Considered   Principally   from   a   Sanitary   Stand- 
point.)   3d  Edition,  Rewritten 8vo,  o« 

Examination  of  Water.     (Chemical  and  Bacteriological) 12 mo,  25 

Merriman's  Elements  of  Sanitary  Engineering     Svo,  oo 

Nichols's  Water-supply.     (Considered  Mainly  from  a  Chemical  and  Sanitary 

Standpoint.)     (1883.) Svo,  50 

Ogden's  Sewer  Design i zmo,  oo 

Prescott  and  Winslow's  Elements  of  Water  Bacteriology,  with  Special  Reference 

to  Sanitary  Water  Analysis I2mos  25 

*  Price's  Handbook  on  Sanitation xamo,  50 

Ricbards's  Cost  of  Food.    A  Study  in  Dietaries 1 2tno,  oo 

Cost  of  Living  as  Modified  by  Sanitary  Science zzmo,  oo 

Richards  and  Woodman's  Air,  Water,  and  Food  from  a  Sanitary  Stand- 
point  Svo,  oo 

*  Richards  and  Williams'*  The  Dietary  Computer Svo,  50 

Rideal's  Sewage  and  Bacterial  Purification  of  Sewage Svo,  3  50 

Turneaure  and  Russell's  Public  Water-supplies Svo,  5  oo 

Whipple's  Microscopy  of  Drinking-water Svo,  3  50 

Woodhull's  Notes  and  Military  Hygiene i6mo,  z  50 

MISCELLANEOUS. 

Barker's  Deep-sea  Soundings Svo,  2  oo 

Smmons's  Geological  Guide-book  of  the  Rocky  Mountain  Excursion  of  the 

International  Congress  of  Geologists Large  Svo  z  s« 

Petrel's  Popular  Treatise  on  the  Winds 8vo  4  oo 

Haines's  American  Railway  Management iamo,  50 

Mott's  Composition,  Digestibility,  and  Nutritive  Value  of  Food.   Mounted  chart.  «s 

Fallacy  of  the  Present  Theory  of  Sound z6mo  oo 

Ricketts's  History  of  Rensselaer  Polytechnic  Institute,  1824-1894.  Small  Svo,  oo 

Rotherham's  Emphasized  New  Testament Large  Svo,  2  oo 

Steel's  Treatise  on  the  Diseases  of  the  Dog Svo,  50 

Totten's  Important  Question  in  Metrology Svo  a  50 

The  World's  Columbian  Exposition  ot  1893 4to,  z  oo 

Von  Bearing's  Suppression  of  Tuberculosis.     (Bolduan.)     (In  press.) 
Worcester  and  Atkinson.    Small  Hospitals,  Establishment  and  Maintenance, 
and  Suggestions  for  Hospital  Architecture,  with  Plans  for  a  Small 

Hospital zamo,  t  25 

HEBREW  AND  CHALDEE  TEXT-BOOKS. 

Green's  Grammar  of  the  Hebrew  Language Svo,  3  oo 

Elementary  Hebrew  Grammar Z2mo,  z  25 

Hebrew  Chrestomathy Svo,  2  oo 

Gesenius's  Hebrew  and  Chaldee  Lexicon  to  the  Old  Testament  Scriptures. 

(Tregelles.) Small  4to,  half  morocco,  5  oo 

Letteris's  Hebrew  Bible Svo,  2  2 

16 


UN! 


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